Spuyten Duyvil Creek is a short tidal estuary at the northern tip of Manhattan, connecting the Hudson River to the Harlem River. Its churning confluence of three water bodies marks where the island of Manhattan separates from the Bronx and the mainland beyond. When Dutch settlers arrived, they found the tidal waters turbulent and nearly unnavigable. The creek flowed in unpredictable surges, fed by Tibbetts Brook from the north, while the Harlem River snaked in an S-shaped course southwest and then north into the East River. During the 17th century, the only way across the Harlem River was a ferry from 125th Street, established in 1667 and run by a local landowner named Johannes Verveelen. Many settlers, unwilling to pay the toll, simply waded or swam across the creek at a shallow point near what is now Kingsbridge in the Bronx.

Frederick Philipse, a merchant from New Amsterdam who had amassed vast landholdings in what was then Westchester County, saw opportunity in the crossing. A bridge eventually replaced the ford, and stagecoach service followed, connecting New York City to the interior. For centuries, Spuyten Duyvil Creek remained the natural boundary between island and mainland, a narrow channel that determined the shape of neighborhoods and the routes of commerce. The Bronx neighborhood of Spuyten Duyvil grew along its northern bank, while Marble Hill settled on the Manhattan side. But the creek's days as a natural waterway were numbered. The completion of the Erie Canal in 1825 and the rise of large steamships demanded a broader passage between the Hudson and Harlem Rivers, one that could handle serious commercial traffic.

In 1876, the New York State Legislature ordered construction of a shipping canal that would bypass the creek's tight turns. The Harlem Canal Company had tried and failed decades earlier; a second company collapsed as well. But this time the state pressed forward. The first section, sliced through Marble Hill itself, opened on June 17, 1895. The consequences were immediate and surreal. Marble Hill, once firmly attached to Manhattan, suddenly sat on the Bronx side of the new waterway. When the old creekbed was filled in with rock excavated from Grand Central Terminal's foundation in 1914, the neighborhood became physically attached to the Bronx mainland. Yet politically, Marble Hill remained part of Manhattan, a geographical paradox that persists to this day. Residents vote in Manhattan elections, send their children to Manhattan schools, and pay Manhattan taxes while walking their dogs in the Bronx.

Further engineering in the 1930s continued to reshape the waterway. Plans finalized in 1935 led to excavation between 1937 and 1938, severing a 13.5-acre peninsula from the Bronx that was absorbed into Manhattan's Inwood Hill Park, where it now houses the park's Nature Center. The Broadway Bridge, a vertical lift span carrying both road traffic and subway trains, links Marble Hill back to Manhattan proper. Today, Spuyten Duyvil Creek, the Harlem River Ship Canal, and the Harlem River form a single continuous channel, collectively called the Harlem River. There is little evidence that the shipping canal ever achieved its commercial ambitions. But the engineering that was supposed to ease the passage of steamships instead created one of New York's strangest civic arrangements: a piece of Manhattan that you can only reach by crossing the Bronx.