A. Peterson's Cooper Union Foundation Building on the north end of the square, the oldest existing American building framed with steel beams, still stands where it was located when it opened in 1859, but the interior was extensively reconstructed in 1975 not only to modernize it, but also to fulfill one of Cooper's plans which was never realized at the time: the installation of a round elevator. The exterior of the building was restored in 1999 as well.

Downtown of the Foundation Building is a small park, Cooper Triangle, which includes