 daguerreotype (c. 1845) courtesy of the Onondaga Historical Association, is on display. So are some cartes de visite of celebrities of the age, which Sojourner Truth sold to raise money for the cause. The New York-based American Anti-Slavery Society's pamphlet used to teach children about the horrors of slavery through the alphabet that begins, "A is an Abolitionist . . . B is a Brother with a skin of somewhat darker hue . . . C is the cotton-field, to which this injured brother's driven. . ."
When war called, 448,850 New Yorkers enlisted in the Union army and 53,000 died in service—the most of any state. New York soldiers accounted for 16% of all Union troops and 11% of the state's total population. Historians believe that New York financed about one-third of the cost of the Civil War. The West Point Foundry provided 27% of the U.S. supply of artillery and projectiles; Burden Iron Works of Troy, 85% of the horseshoes.
While no battles were fought in the Empire State, depots readied regiments of soldiers in Buffalo, Elmira and New York. A photograph from the Library of Congress shows the Irish Catholic Forty-Eighters—one of the 23 ethnic regiments of Union soldiers—at Mass. Thirty percent of New York's soldiers were foreign born.
Compelling objects in the exhibition include a restraining chain from the Elmira Prison Camp where rebel soldiers were detained, a ledger book for the 43rd New York volunteers, a military medical kit with dried blood, and cross-stitched potholders celebrating the Emancipation Proclamation.
The conclusion to the show, like its antebellum introduction, commands attention. Ulysses S. Grant, who tried to enforce civil-rights laws as president, moved to Manhattan in 1881 and died in rural Saratoga County in 1885.
On display is the wicker chair from the Wakefield Rattan Co. that he used while working on his memoirs just days before his death. And the postwar block has a small low-tech monitor flashing images of the 400 or so monuments across the state dedicated to Civil War heroes. Among the most celebrated is the one to Douglass in Rochester, where he resided and published his newspaper, the North Star.
The final scenes of "An Irrepressible Conflict" poignantly reflect achievements and challenges in advancing the civil-rights cause beyond the war. In Buffalo in 1905, W.E.B. Du Bois founded the Niagara Movement, laying the groundwork for the NAACP's birth in Manhattan only a few years later. A photograph captioned "a flag announcing a lynching was flown from the widows of the NAACP headquarters on 5th Avenue in New York City, 1936" is juxtaposed with a 1920s Klan robe and hood from Greene County, N.Y.
The exhibition reveals New York not only as indispensable to the Union (and to its ultimate victory) but also as essential to the continued pursuit of justice among the formerly enslaved and their descendants. It admirably realizes its objective: To establish New York's significance in the Civil War and its lasting battle for freedom.
Mr. Heffner is a writer in New York.