Due to Ambrose's lobbying in Washington, the government appropriated money in 1881 to dredge channels near the Brooklyn waterfront from 8 feet to 40 feet. (You're welcome, Bay Ridge and Red Hook.) In the 1890s, he successfully lobbied to have the channel from Sandy Hook to Manhattan (about 7 miles) dredged from 10-20 feet to 40 feet deep and 2,000 feet wide. He died in 1899, before the work was completed; Congress voted to name the passage the Ambrose Channel in 1902. (The channel was recently blasted down to 50 feet, to allow for the larger boats coming through the newly enlarged Panama Canal.)
Until 1967, the Atlantic end of the Channel was marked by a floating beacon known as the Lightship Ambrose. The last incarnation of it is now docked at South Street Seaport.
Soon after Ambrose's death, his friends gave a bronze bust of him to his children; they in turn gave it to the City of New York in the 1930s. Robert Moses had his chief architect, Aymar Embury II, design a setting for it. Frederick G. R. Roth (of Balto fame) sculpted a relief map of the Ambrose Channel.
In 1990 the bust was stolen. There has been talk for years about making a new one.