The building now known as 51 Walden was constructed in 1887 to serve as the town armory. It is listed on the National Register of Historic Places and a commemorative brass plaque was unveiled at a ceremony on Veterans Day, November 11, 2007. 

Concord architect John Chapman drafted the plans for a Town Armory in 1887, which included a head house and drill shed. It was built in the shingled Queen Anne style, with overtones of the Romanesque. A fire damaged the building in 1912, but the town repaired the structure in 1920 and renamed it The Veterans Building.

In 1922, eminent Boston architect C. H. Blackall designed a stage, which was constructed at the back of the building. The total cost of $11,900 was shared by the Town and the Concord Players, which was founded in 1919. The stage is a smaller version of the stage in Boston’s Colonial Theatre; it includes a fly tower that allows scenery to be moved in and out easily by means of counterweighted rigging. Complete with proscenium arch, the stage is raked from back to front, which helps audiences to view performances.

For the next fifty years, the Concord Players used The Veterans Building for theatrical performances. The Concord Minutemen and the American Legion had offices in the building as well, and at various times dog training classes were conducted on the site.  Though some modifications and repairs were made over the years, the facility deteriorated and was actually slated for demolition in 1958, but Town Meeting failed to approve sufficient funds to tear it down.  Despite its condition, the Concord Players continued to stage its performances in the building for the next decade, and the structure also functioned as a youth center.

In 1972, the Friends of Performing Arts in Concord (FOPAC) was incorporated as a 501(c)(3) Massachusetts charity with the goal of renovating the building and operating it as a center for the performing arts.  Funds were raised and the lobby, dance studio and main hall were reconfigured for public performances. In 2015 the name was changed to 51 Walden, which leases the building from the town for $1 a year, and is responsible for management, repair, and maintenance.