142 A HISTORY OF AMERICA IN 100 MAPS
In 1856 John Jay captured the urgency of the sectional
crisis by starkly differentiating “America free, or
America slave” (page 140). Four years later, those
divisions were realized when Abraham Lincoln was
elected president without any Southern support.
Within weeks of Lincoln’s victory, South Carolina
had seceded from the Union; by February 1, seven
states of the Deep South had followed, and together
they formed the Confederacy. Lincoln took office
in early March, and used his inaugural address to
defuse the crisis by reminding Southerners that he
had yet to take any action against slavery. For a time
he kept the states of the upper South in the Union. In
April, however, South Carolina attacked Fort Sumter,
prompting Lincoln to call up a volunteer militia to
suppress the rebellion. Many Virginians considered
this a hostile act by the federal government,
and voted to join the Confederacy. Within weeks
Arkansas, North Carolina, and Tennessee had
followed.
The secession crisis prompted the nation’s military
and civilian agencies to mobilize for war. The US
Coast Survey harvested its extensive knowledge of
Southern coastlines and harbors to prepare for a
potential blockade. The Coast Survey also sent its
men into the field to refine its understanding of
both terrain and waterways, producing thousands of
detailed charts to aid Union strategy. But even before
the war began the agency had been a crucial source
of experimental maps.
Among the most impressive of these were two
groundbreaking maps of the distribution of slavery.
The first profiled Virginia, and the second—shown
here—covered the entire South. The map elegantly
and innovatively used shading to indicate the density
of the slave population in each county. While Jay’s map
on the previous page simply divides the country into
two categories, the Coast Survey map reveals a far
more complex and varied geography of slavery. Darkly
shaded areas throughout the cotton belt and the Lower
Mississippi River show high dependence on slavery,
while lighter areas indicate its relative absence.
The Coast Survey’s map was used to raise money
for the Sanitary Commission, a civilian volunteer
organization founded in 1861 to support the Union
Army. The Superintendent of the Coast Survey—
Alexander Dallas Bache—served as the Commission’s
SLAVERY, SECESSION, AND WAR
US Coast Survey, “Map Showing
the Distribution of the Slave
Population,” 1861
treasurer, and no doubt provided the map for this
fundraising effort. Its implicit message is that slavery
caused the rebellion. At a glance, it is clear that the
states of the Deep South that led secession were also
those with the highest concentration of slaves. This
message is reinforced by the table at the bottom
of the map, which lists states according to their
dependence upon slavery. This hierarchy almost
precisely corresponded to the order in which the
states left the Union. All of these cues embedded in
the map reminded the public that the rebellion was
driven by slavery.
The Coast Survey’s decision to experiment with
this type of statistical mapping shaped the uses of
cartography during and after the Civil War. Among
those who helped to create the map of slavery was
Captain William Robert Palmer, an engineer with the
Corps of Engineers who worked for the Coast Survey
during the war. Palmer sent copies of the initial map
of slavery in Virginia to military leaders as well as
to members of President Lincoln’s cabinet. Lincoln
himself was captivated by the map of the South, and
kept it close at hand.
In the president’s mind, the map revealed the
strengths and weaknesses of the Confederacy in a
way that topographic maps could not. While many
viewers were drawn to the dark spaces on the map,
Lincoln used it to understand that the Confederacy
might be most fragile in areas where slaves were
absent. For instance, in the early months of the war
the president held out hope that a railroad from
Kentucky toward the Cumberland Gap or Knoxville
might provide a lifeline to Southerners in eastern
Tennessee who staunchly resisted the Confederacy.
More generally, a map like this reinforced Lincoln’s
belief that secession had been imposed upon the
South by a minority of slaveholders. With time and
resources, he argued, the Confederacy might be
overturned from within.
We know of Lincoln’s close attention to this map
through the diary of the painter Francis Bicknell
Carpenter. In September 1862 Carpenter read about
Lincoln’s preliminary Emancipation Proclamation,
which gave the military the power to liberate slaves
as it moved through the rebel states. Carpenter
was deeply moved by Lincoln’s announcement, and
believed it to be of national and moral importance
second only to the Declaration of Independence. As
an artist, he sought to capture the moment when the
president revealed the plan of emancipation to his
cabinet. Not only did Lincoln agree, but in early 1864
he invited Carpenter to set up a studio in the White
House. The portrait that resulted is featured on the
next page.