Coast Survey’s Civil War Maps and Fieldwork

To mark the 150th anniversary of the Civil War, NOAA’s Office of Coast Survey examined its archives and uncovered a rich collection of wartime maps, charts and firsthand accounts. These records document the work of topographers and hydrographers who operated alongside Union forces as surveyors, boat pilots and chartmakers, often under dangerous frontline conditions.

Coast Survey personnel served in both combat-intelligence and combat-engineering capacities. Field teams scouted and mapped terrain, made soundings, piloted ships through hazardous waters, cleared sunken vessels from channels and installed navigation aids — frequently while under fire from enemy artillery and small arms.

“Most of the people in the Coast Survey were civilians,” said Coast Survey spokeswoman Dawn Forsythe. “They didn’t wear a uniform and could be summarily shot as spies. This was definitely a risk they faced.” Many surveyors fell ill from disease, and some died from battlefield wounds, as recorded in NOAA’s official history, The Coast Survey.

The Coast Survey traced its origins to 1807, when President Thomas Jefferson founded the organization to produce nautical charts for maritime safety, defense and boundary determination. When the Civil War erupted, the agency nearly lost funding to the Army and Navy. Its superintendent, Alexander Dallas Bache — a prominent scientist and descendant of Benjamin Franklin — preserved the organization by directing its resources to support Union operations. Bache’s strategy leveraged the Survey’s mapping expertise and the local knowledge of its skilled boatmen to create the maps and charts Union commanders urgently needed.

Historians note that many generals quickly recognized the value of Coast Survey teams. They dispatched crews on reconnaissance patrols to sketch battlefields and map fortifications. One notable example is J.S. Harris’s sketch of Fort Jackson, which guarded the southern approach to New Orleans on the Mississippi River; that sketch is still regarded as a fine work of field cartography.

What had once been a relatively quiet scientific pursuit became hazardous work. Mapping and charting teams often operated at night behind enemy lines to collect data for naval operations scheduled the following day. As federal employees working in seceded or hostile states, surveyors sometimes faced seizure or arrest. In the Florida Panhandle, F.H. Gerdes, leading a survey party in Pensacola Bay, feared his vessels might be captured as tensions escalated. He redirected his ships to New York City when conditions deteriorated. Survey operations by vessels such as the schooner Peirce on Florida’s Indian River and Torrey on St. Joseph’s Bay were likewise halted due to local hostility.

Some Coast Survey vessels were seized by Confederate forces. South Carolina captured the Petrel and Fire Fly shortly after seceding. The Confederates later burned Fire Fly in Savannah in 1864 to prevent recapture. Petrel was refitted by Charleston entrepreneurs as a privateer and, during its first engagement in mid-1861, was sunk by the Union frigate St. Lawrence.

Individual surveyors also endured personal peril. P.H. Donegan, a tide observer at Calcasieu Pass, Louisiana, found himself stranded when the survey vessel Twilight was seized at Port Aransas, Texas. Captured and accused of espionage, he was confined to a small cell for four months before his release in November 1861, reportedly through intervention by the British consul.

Other incidents highlight the close cooperation between Navy commanders and Coast Survey personnel. In November 1861, Charles Boutelle, serving as hydrographer to Rear Admirals Samuel DuPont and John Dahlgren of the South Atlantic Blockading Squadron, rebuoyed the channel at Port Royal Sound near Beaufort, South Carolina, despite fire from a Confederate naval squadron. He then piloted five Union warships through the channel aboard the Coast Survey steamer Vixen so they could bombard and capture Forts Beauregard and Walker.

During the siege of Vicksburg in February 1863, surveyor Clarence Fendall reported working perilously close to enemy batteries. “Yesterday, I was three miles beyond our pickets and within 600 yards of the enemy’s batteries,” he wrote. Cannonballs struck the ground within 20 feet of his team as they continued their survey work. Fendall later produced the map “Approaches to Vicksburg,” which assisted Union operations there.

In advance of the April 1862 bombardment of Fort Jackson, Coast Surveyors established reference points and surveyed the riverbanks to support indirect artillery fire. Harris recalled being under fire from Confederate gunboats while conducting river surveys and recognized the risk of being treated as a spy because he carried no military identification.

Beyond tactical support, the Coast Survey provided strategic intelligence. Under the leadership of Bache, a Blockade Strategy Board produced an eight-part “Notes on the Coast of the United States,” a military-oriented guide containing sailing directions for warships, more than 100 maps and charts, and detailed geographic information for the Southeast and Gulf coasts. These materials directly supported blockade operations and amphibious assaults.

The Coast Survey also produced an influential 1861 map of the southeastern United States that used shading to show the distribution of the slave population, based on the 1860 census. This map is considered an early example of using cartography to portray social and political statistics. Edwin Hergesheimer, head of the Survey’s drawing division and an ardent abolitionist, oversaw the map’s production. Historians note that the map was intended to visually connect slavery and secession and that President Abraham Lincoln reportedly consulted it as he developed strategy.

NOAA’s Office of Coast Survey has made its Civil War Collection available online, including nearly 400 historical maps and charts that document the Survey’s contributions to the war effort and the hazards faced by its civilian staff. The collection offers a compelling record of how scientific surveying, charting and local maritime knowledge shaped naval operations and military strategy during the Civil War.

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This article originally appeared in the December 2011 issue.