President Bush won only 24% of the vote in New York City in 2004. Abraham Lincoln did not do much better. In 1860, the president many of us regard as America’s greatest won less than 35% of the city’s vote. In 1864, he won even less — about 33%. Why most New Yorkers did not care for Lincoln is a question that will be answered to most visitors’ satisfaction in “New York Divided: Slavery and the Civil War,” a well-designed, richly informative exhibition opening today at the New-York Historical Society.

“New York Divided” follows last year’s “Slavery in New York.”That exhibition told the story of the slavery that remained legal in New York State until 1827. The current exhibition takes us on a journey from the 1830s to the immediate post–Civil War period. Although slavery had been abolished in New York, the city’s economy was as dependent upon slavery as ever. New York City had such close ties to the Southern plantation economy that as Southern secession loomed, Mayor Fernando Wood seriously proposed that the city secede from New York State to be able to carry on our lucrative commerce with the South.

New York was cotton broker to the world at a time when cotton amounted to half of all American exports. New York merchants innovated at a furious pace to maintain the city’s indispensability to plantation owners. In 1818, the Yorkshire-born Quaker merchant Jeremiah Thompson inaugurated the Black Ball Line, the first regularly scheduled transoceanic (and intracoastal) packet shipping service in history. He thus became, as Robert Albion pointed out in his classic 1939 book “The Rise of New York Port,” the pre-eminent cotton exporter in the country — and one of its richest men.

As “New York Divided” shows, New York merchants not only innovated, they also placated Southerners’ sensibilities. The exhibition has a startling display of four plates and a pitcher manufactured for a New York hotel by porcelain makers in Staffordshire, England. The dishes bear images of pleasant Southern life, meant clearly to appeal to the hotel’s many Southern guests. The dishes demonstrate the complex interdependence of Southern plantations, New York businesses, and the English factories where much of the cotton went. The cotton returned to us from abroad in the form of cloth and clothes — and this exhibition abounds with cotton, beginning at its entry point by bales suspended from the ceiling.

New York, of course, eventually began to replace those imports and to utilize the Southern cotton in our own factories, developing the legendary New York garment industry. Indeed, early New York clothing manufacturers profited by provisioning Southern plantations. And it wasn’t just New York shippers and manufacturers (and their laborers) who profited from the Southern trade, but also the bankers, lawyers, auctioneers, insurers, and others. All the plantation owners did was watch the cotton get picked. New York took care of the rest.

In this atmosphere, it’s not hard to see why, in spite of our own abolition of slavery, it was important to so many white New Yorkers to perpetuate the notion of black inferiority. “New York Divided” provides many examples of how blacks in New York were second-class citizens, frequently vilified and caricatured, and held in a low moral esteem even by anti-slavery leaders like the newspaper editor Horace Greeley.

The exhibition provides a counter-image by its emphasis on James McCune Smith. Born in New York City in 1813, Smith was a slave for the first 14 years of his life, until abolition in New York State in 1827. He attended the city’s African Free School, where he reveled, and excelled, in his studies, and decided to become a doctor. Columbia would not admit a black man, so with the assistance of others he went abroad, earning his B.A., M.A., and M.D. (1837) at the University of Glasgow, finishing first in his class at each stage. Back in New York, Smith established himself as a physician and became staff doctor to the Colored Orphan Asylum. (One of the splendid artifacts on display is an admissions book from the asylum.) Smith also became one of the most eloquent and influential abolitionists in New York. The exhibition makes clear that he was one of the greatest New Yorkers most New Yorkers have never heard of.

Helping out are specially commissioned videos of the actor Danny Glover portraying Smith. Usually I am resistant to the use of multimedia in museum exhibitions. Here, however, the videos are low-key, intelligently designed, and truly aid in helping us to grasp the times. In addition to the Glover videos, I was much taken by a film of African-American historian Professor Nadine Graves-George coaching contemporary young actors in the principles of minstrelsy, so we can see for ourselves why this stage form was both so offensive and so popular. She also coaches a dancer in performing in the style of William Henry Lane, known as Master Juba, the Fred Astaire of the Five Points. Lane’s dancing electrified audiences, both black and white — not least Charles Dickens, whose 1842 “American Notes” contains a pop-eyed description of Lane’s dancing. As an inventor of tap dancing, Lane combined the Five Points’ dual Irish and African cultures in one of the great examples of urban synergy.

Alas, whatever cultural cross-fertilizations may have occurred among the blacks and the Irish, they could not prevent the tragic draft riots of 1863. “New York Divided” contains much material on the riots, as one would expect, but does not overdo it, reserving space for lesser known aspects of the times. (Barnet Schecter’s fine new book on the draft riots, “The Devil’s Own Work” [Walker & Company, 448 pages, $28] is a good supplement to the exhibition.) Two artifacts related to the draft riots may take your breath away. One is a beautifully crafted draft wheel used on the first day of the draft lottery in New York, July 13, 1863. The other is a Brooks Brothers army dress coat, said to have been worn by Lt. Col. George Schermerhorn of the elite 7th Regiment when he was called in to help put down the riots.

Many people contributed to “New York Divided,” but major credit goes to curator Richard Rabinowitz and his American History Workshop, which produces public exhibitions and interpretive presentations. He and the society have given us a wondrous chunk of essential New York history, a superb pendant to the Metropolitan Museum of Art’s epic “Art and the Empire City” of a few years ago. I will be returning to “New York Divided.”

Until September 3 (170 Central Park West at 77th Street, 212-873-3400).