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If you plan to shut down Atlanta and march to the sea, it helps to know how to get there.

William Tecumseh Sherman looked south from the Tennessee heights of Lookout Mountain with Captain Orlando Poe, his chief engineer and topographer. Far below, the rugged terrain of northern Georgia softened beneath an endless canopy of trees— scrub oaks, pines, chestnuts and cedars. Brown rivers and red clay roads were barely visible on this late April day in 1864. A single line of the Western & Atlantic Railroad made its way sturdily along, under the trees, across the rivers, through the ridges and hills. It was the one man-made feature in their range of vision.

Sherman commanded the Union armies of the Ohio, the Tennessee and the Cumberland; more than 100,000 men. They were veterans, well equipped, full of confidence. Sherman’s task, as outlined by his commander and friend Ulysses S. Grant, was to begin a campaign against Atlanta in the first week of May. The operation was to be coordinated with other Union forces, including the Army of the Potomac in the Eastern theater.

Atlanta, 100 miles to the south, was the Confederacy’s western railroad, supply and manufacturing hub. Its importance stemmed from its remote inland location and its reputed inaccessibility to Union armies.

Twenty years earlier, Sherman had traveled the region from Marietta, Ga., to Chattanooga, Tenn., investigating possible fraud and expense claims for the U.S. Army. The general would later write that this experience had been “of infinite advantage” in the campaign about to unfold. Sherman could remember terrain features and topography the way other people remembered faces. He had a general idea of what to expect as he planned his path through the sparsely populated wilderness that was to be his field of operations.

“Give me enough men and time to look over the land and I’m not afraid of the devil,” the fiery general reportedly once said. As things now stood, he had enough men and he’d had his look at the land. And the devil was also at hand: Confederate General Joseph E. Johnston had 60,000 men entrenched a few miles south at a ramshackle Georgia hamlet called Resaca.

As he paced back and forth, did his thinking, smoked his cigars and stared south, Sherman had another image of northern Georgia fixed firmly in his mind. On a standard G. Woolworth Colton map of the United States, Grant had drawn in thick blue pencil an outline of the campaigns he intended his separate armies to wage. Grant meant to close out the war by moving all his forces simultaneously and systematically against the beleaguered forces of the Confederacy. Grant explained his strategy in six words: “They have not got army enough.”

When Sherman saw this graphic presentation of Grant’s intended strategy, he was ecstatic. “From that map I see all,” he said. “This speaks volumes.”

Fully understanding his place as a pillar of Grant’s plan, Sherman got busy with his own maps. He had inherited the Union’s best topographical engineering department when the Army of the Cumberland fell under his command that spring. This department’s preeminence was the direct result of the priority Generals William S. Rosecrans and George H. Thomas gave to military mapping. Thomas’ 1862 victory at Mill Springs, Ky., had been achieved despite a harrowing series of miscues that maps could have prevented. Thomas resolved thereafter to make reliable maps a centerpiece of his preparations.

One important change was to make mapping a dedicated command. Topographical engineers in the Army of the Cumberland were given a single duty. They were not used as aides, couriers, scouts, guides or spies. They did not select bivouacs or set out latrines. They prepared and produced maps. And there was no general in the war better able to appreciate their efforts or to use their maps more effectively than Sherman.

Sherman’s charge was to maneuver south, with Atlanta as his initial objective. That Atlanta’s remoteness was the key to its strategic importance illustrates the challenges Sherman faced: So forbidding was the topography of northern Georgia that its defender, Joe Johnston, had neither the resources to map it nor a strong inclination to try. Johnston’s personal reconnaissance of the terrain was limited to the trips he made back and forth on the Western & Atlantic Railroad. Jefferson Davis would rebuke Johnston, writing that, “In failing to inform himself of the terrain in his rear” Johnston “had neglected the primary duty of a commander.”

The principal feature in the campaign Sherman devised was the single track of the railroad. On a map, the railroad ran staunchly through a wilderness of mountains, forests, rivers and streams, with stops at occasional rude clearings containing tumbledown settlements. This was to be Sherman’s strategic plumb line and his tactical lifeline. It would be taxed to the utmost (a problem of “pure war,” observed one contemporary) to supply 100,000 men in that most wasteful of endeavors, a military campaign.

This utter dependence on the railroad severely restricted Sherman’s options. He could shift from one side of the railroad to the other, but he could never stray far and he could never cut loose. Joe Johnston was fully aware of Sherman’s limited options and knew that all he had to defend was this narrow railroad corridor. Sherman was thus confronted with a war of maneuver, the sort of war that must be conducted with reliable maps. The maps would have to be more reliable and far more detailed than any recollections Sherman may have had of his long-ago trek.

The mapmakers faced daunting challenges. They were operating in unfriendly and unfamiliar territory, which made reliable topographic information difficult to credit and dangerous to get. The size of their armies meant that multiple, practicable roads had to be found so the forces could operate separately but in the same general direction, and be able to come to one another’s aid when necessary.

Innovation, standardization and organization were therefore the order of the day. Sherman’s topographical engineering departments worked quickly and efficiently to gather data, map it, print it and distribute it.

Their initial effort was to collect any available maps of the area. This didn’t amount to much in northern Georgia since there weren’t many maps, and none of them were much good: minimal at best, fanciful at worst. Sherman held up his campaign for two days while he waited for a copy of a northern Georgia map just published by the U.S. Coast Survey, the Union’s premier civilian mapping agency. It was small scale, meaning it covered a large area but without much detail, but from those sorts of maps and from general observations, it was possible to put together what was known as a “skeleton” or information map. This map would contain the most basic, unchanging and recognizable features in the landscape: the hills, towns, rivers, principal roads and railroads.

Once these elements were drawn in, it became the job of the engineers—with the help of cavalry, scouts and other reconnaissance efforts—to flesh out the details of the map.

One of the most dramatic accounts of this process came from a short story by Ambrose Bierce published after the war but clearly based on his own experiences. He wrote impressively of estimating distances by the fact that he was still alive and of “thundering” cavalry charges staged so that he could gain brief access to and evaluate a fording site or an important intersection.

Less exciting but equally valuable were the interrogations conducted by men with a particular knack for eliciting information. Especially adept was Sergeant N. Finegan of the 1st Ohio Infantry. He would engage in lengthy, friendly conversations with a network of local residents—refugees, slaves, peddlers, preachers, country doctors, farmers; anyone likely to have special knowledge of the territory ahead. Carefully phrased intelligence questions were carelessly worked into otherwise innocuous conversations. It appears to have been an especially effective way of gathering intelligence in sparsely populated areas where gregarious locals were often starved for conversation.

Engineers who mingled with soldiers on the picket lines used similar techniques. They monitored the gibes and gossip carried on with the Rebel pickets on the opposite side of a river or the far edge of a clearing. Pickets would typically be standing watch at fording sites, byways and other obscure but tactical points. When exchanges of tobacco, coffee and newspapers were carried on, the unsuspecting Confederates would reveal a place to ford— which would be duly noted on the skeleton map.

Engineers also were supplied with a list of the names and whereabouts of local civil engineers, who were tracked down and relieved of any maps they might have on their premises. Town halls and courthouses were similarly visited and their cartographic resources were likewise seized. Some of the maps Sherman relied on as he planned his March to the Sea, for example, had been discovered in Atlanta’s town hall after the city had fallen to Union forces in September 1864.

Tax maps were especially handy because they showed individual lot numbers. Engineers standing beside a remote cabin could determine their precise location by referencing the inhabitant’s tax records. It was a 19th-century equivalent of a GPS system. Anything of interest in the immediate surroundings could then, with reliable accuracy, be added to an ever-improving military map.

On the march, topographers divided their duties. One surveyed the main road, one compiled the bearings of prominent features (these might be stands of pine trees or a graveyard, or a church), and one checked out side roads. They were more interested in their surroundings than in accuracy. A steep grade or a muddy-bottomed ford was of much greater concern than exact distances or correct angles. The main concern was to keep the men, wagons, ambulances and artillery moving in the right direction while maintaining contact with the units deployed on either side of them.

The engineers used this new information to fill in the skeleton maps. All sorts of unexpectedly nitty-gritty logistical details were required to meet the map needs of a 19th-century army, powered by feet and hooves and largely dependent on what the men could find along the road for their food and water.

The locations of springs and wells, the crops in the adjacent fields, the orchards, taverns, blacksmith and wheelwright shops, the makeup of the roads, the farms, barns, plantations and the names of the residents along the march route were all of interest. The residents’ names were painstakingly documented because they provided reliable frames of reference on roads that were often nothing more than farm lanes or paths.

Another mapping resource was the local knowledge of Georgia’s slaves. Their limited but intimate familiarity with their immediate surroundings would prove invaluable to the Union mapmakers.

The 1860 Census map of Georgia and Alabama was also particularly helpful as Sherman planned his march. The map contained detailed and county-by-county population and agricultural data, and Sherman could study normal map features as well as population figures and the racial profile of the residents, crop figures by the bushel and bales, livestock and other data critical to a general who was cutting loose from his supply base and intending to live off the land. Set before him was the region’s bounty: the bushels of corn, the gallons of sorghum, and the number of horses and mules. From this one map, Sherman could determine not only where he could best sustain his own armies, but where he could simultaneously do the most damage to the Georgia economy.

He carefully scheduled his route so he would be marching in the midst of the 1864 harvest. Finally, adding psychology to logistics, he waited for President Lincoln’s triumphant re-election to demoralize the South before he made his own contribution to the demise of the rebellion.

When all the information had been gathered and transferred onto the maps, Sherman’s topographical department mastered the next prerequisite of an effective mapping organization by quickly duplicating and distributing the maps that had been drawn. As the Union armies advanced on Atlanta, engineers set up their cumbersome lithographic presses at each accessible stop along the railway. Using special “autographic” ink (a normal lithograph would have printed a map backward,) they quickly printed copies of a “right-reading” map. Erasures were easily made with a swipe of a cloth and corrections made with a grease pencil. The maps could be printed on paper and cloth, even on muslin handkerchiefs.

Critical to Sherman’s control of his scattered forces was the fact that staff and field officers all had the same map. Orders were given and reports were received with identical topographical frames of reference. Thus, even if the map was wrong, it was wrong in the same way for everybody. And that was the next best thing to being right.

When Sherman set out in early May 1864, each of his army, corps, division and brigade commanders had the same map, or details of the same map, in his possession. Every one of them had a superior map and a better understanding of the lay of the land than any of their Confederate counterparts who were trying to defend it.

Cavalrymen carried maps folded up in their saddlebags or pockets. Maps were even printed on neckties and shirts, precursors of the World War II “escape maps” issued to airmen. Small question marks representing blank areas appeared on the maps; anyone with information was asked to draw it in and pass the map back. The new information would be quickly inked in and a new, updated map would be issued.

Engineers would print comments or queries on the maps (an amusing example: “Unable to find Lost Mountain”). The idea was that each map was a work in progress, always improving, and the map’s content reflected that. As the men advanced, the blanks were filled in with firsthand, reliable data. Roads that had been surveyed were shown in double lines. Broken lines indicated a road less certainly known. All the maps used uniform symbols, so a bridge was always a bridge, a ford a ford, a house a home.

When the lithographic presses were not available, a photographic method of reproduction known as “sunprinting” was used to supply updated maps. The Georgia sun beating down on a heavily inked map drawn on translucent paper created a negative image on a piece of treated paper placed beneath it. The resulting image was slightly murky, but a set of serviceable maps was the result. The topographical engineers also had a staff photographer, George N. Barnard, to photograph maps, landforms, fortifications and other sites of interest.

Relying on all of these expedients, the Union maps got better and better as the armies advanced. The best, in fact, on either side in the Civil War.

Orlando Poe estimated that 4,000 maps were supplied to the armies between May and September 1864. Some 19 different maps, not including skeleton maps, were published. When a formal topographical engineer’s headquarters was set up in Marietta, Ga., in July 1864, 1,000 sheets of 14 different maps were issued, six of them new. Poe realized that the whole mapping operation was inexpensive, too. He figured that he spent less per month than it cost the army to purchase and maintain a single “sixmule team complete.”

Even with the state-of-the-art maps, however, Sherman’s generals sometimes blew golden opportunities. The first and most egregious failure was committed early in the campaign at Resaca by Maj. Gen. James Birdseye McPherson, commander of the Army of the Tennessee. Sergeant Finegan of the 1st Ohio discovered a strategic pass called Snake Creek Gap that the Confederates had overlooked. McPherson slipped his army through the pass and showed up undetected behind the entrenched Rebels. But rather than press his advantage, McPherson hesitated, and the moment was lost.

Sherman’s progress from Chattanooga to Atlanta was, as he characterized it, “a big Indian war.” His maps allowed him to loop from one side of his railroad supply line to the other, screened from enemy observation by the heavy woods, yet free to maneuver because of his map knowledge.

The march from Atlanta to Savannah and the sea, sometimes perceived as a swashbuckling adventure, was in fact a triumph of careful planning, intense and innovative preparation and masterful execution. The advance moved along so steadily and with such speed that the civilian engineers from the U.S. Coast Survey accompanying the march had neither the chance nor the necessity to prepare the accurately scaled, elaborately detailed maps they were capable of producing.

Nor was Sherman’s version of a scorched earth policy the result of devilry on the general’s part. With a Confederate army still active behind him, he had to sustain his own armies and then make certain there was nothing left for a pursuing army to live on. (It’s worth noting that he was also making it impossible for his own armies to hesitate, fall back or retreat.) His ultimate strategy was to wreak as much havoc as possible on the military resources of the Confederacy, which was rapidly disintegrating as a nation and had become nothing more than a military camp for an army of generals. In any event, the legend of Sherman’s destruction was shown by David J. de Laubenfels to be greatly exaggerated in the 1950s. He used Sherman’s military maps to prove that many of the plantations that had supposedly been wrecked were in fact the victims of termites, neglect and time.

Sherman was clearly best at Jominian strategy, which stressed places rather than armies, and put a premium on solving problems in an orderly way through thorough planning, topographical expertise and careful logistics. Yet if, as Antoine-Henri Jomini asserted, strategy takes place on a map, success and victory have to happen on the ground. It takes “boots on the ground,” in the modern parlance, to unequivocally confirm that a given strategy is a success. With the blue penciled lines on his G. Woolworth Colton map, Grant hoped to have Sherman’s army, in a different theater of the war, affecting Lee’s army in Virginia. Lee’s lieutenant, James Longstreet, besieged at Petersburg, had more pickets—more “boots in the ground”—facing Sherman, who was 100 miles away, than were facing Grant and Meade, 100 yards away.


Cartographer Earl McElfresh is the author of Maps and Mapmakers of the Civil War (Abrams, 1999) and owner of McElfresh Map Co.

Originally published in the May 2009 issue of America’s Civil War. To subscribe, click here