Brush Square was designated as one of four original public squares in the 1839 Waller Plan for the City of Austin. It was named in 1888 after a prominent Austin merchant and in 1928 was zoned to be neighborhood park land.

However, parts of Brush Square have been used over the years as a public market, temporary railroad depot, and the Alliance Cotton Yard. In 1934, the O. Henry House (built in 1888) was relocated from nearby 4th Street to be a museum, followed in 1939 when Fire Station #1 was built on the western half of the Square. Finally, the Susanna Dickinson-Hannig House, built in 1869 just to the east of Brush Square, was relocated in 2003, completely restored, and opened again in 2010 as a museum. Both houses are now listed with the National Register of Historic Places.

Although still in active use by the Fire Department, today part of Fire Station #1 houses the Austin Fire Museum, a collection of early City of Austin fire fighting equipment, photographs, uniforms, and memorabilia. It is proposed that one day, when the Fire Department operations cease, the entire historic 1939 building could become a multi-purpose Firehouse Museum (p. 74, Downtown Austin Plan, Parks and Open Space Master Plan, 2010).

The residual open green lawn and courtyard between the O. Henry and Dickinson Museums, shaded by several exceptional Live Oak trees, is used several times a year for organized public and private events, including the annual O. Henry Pun-Off World Championships and the SXSW Film, Interactive, Music Festival. Foundation board members have been instrumental in planning a long-term park vision and finding money for new Brush Square landscaping.