New York has two Roman-style triumphal arches that I know of: at Washington Square in honor of George Washington, and at Brooklyn’s Grand Army Plaza in honor of the Union army of the Civil War. (There could well be others, but if there are, they’re fairly obscure.) There was a temporary third in 1919, spanning over Fifth Avenue at Madison Square, as seen by Underhill above. This was a victory arch for the end of World War I, which was, in my opinion, hardly justified by the extent of US involvement in the war.
The obelisk at the right side of the arch was permanent and has a more interesting story. It was built in 1857 in honor of General William Worth, and unlike the vast majority of monuments in New York it is not a cenotaph. Worth is actually interred below the monument. Since the BMT subway was built, cut-and-cover, along the immediately adjacent stretch of Broadway just about sixty years after the monument was dedicated, I imagine that Worth has had a lively time for more than a century.