Rittenhouse Square is a neighborhood centered around one of William Penn's five town squares. The square was originally called "Southwest Square", for being the southwestern square in Penn's layout of the city. In 1825, the square was renamed after David Rittenhouse, who was a clockmaker and astronomer. Rittenhouse surveyed the Pennsylvania-Maryland border from 1763 to 1764, and his survey was used by Charles Mason and Jeremiah Dixon later on. Rittenhouse also was a member of the state General Assembly and Constitutional Convention.
Rittenhouse Square began as a wealthy area when the first mansion was built on Walnut Street in 1840. Land surrounding the square was developed in the mid- to late 1800s, with brownstones, townhouses, and mansions. While some houses are now used as apartment buildings or offices, and highrises were built up along the square in the 1900s, the neighborhood is still a desirable address.
Buildings on Walnut Street, facing Rittenhouse Square. The Van Rensselaer House, on the right, was built in 1898. It was the home of Alexander Van Rensselaer, who financed the Philadelphia Orchestra. The Alison Building, built in 1924, is on the left.