|Starting in the mid 1850s, downtown Pittsburg grew to become an important commercial center in an area based largely on an agricultural economy. The Pittsburg Commercial Historic District includes historic commercial properties that retain architectural integrity, reflecting the historic character of the Pittsburg community and its development from the 1860s through the 1960s. The Pittsburg downtown area embodies the distinctive characteristics of many styles of commercial architecture, and the appearance and overall feeling of the district has changed very little. The Pittsburg Commercial Historic District is nominated under Criterion A in the areas of Commerce and Community Planning and Development, and Criterion C in the area of Architecture, at the local level of significance. The period of significance spans from 1862, which is the date of the earliest extant resource in the district, to 1965, which corresponds to the construction date of the four newest contributing properties within the district boundary.