Chester Lyman mapped the square in 1848, and it was landscaped from the late 1860s; a fountain went in at its center in 1885, when people began calling it a park. The McKinley statue of 1903, Trinity Cathedral and the First Unitarian Church stand on or beside it, and Robert F. Kennedy spoke there in 1968.
North Second Street was cut through the park in 1955, and light rail runs along it. The park and nine buildings around it form the St. James Square Historic District, listed in 1979.