In 1963, concerned about the rapid development in the Amador-Livermore Valley, local residents organized to preserve the regional history of the area. The Amador-Livermore Valley Historical Society (ALVHS) was founded on April 18, 1963 and began its decades-long effort to protect, preserve and interpret the history of the valley. The Amador-Livermore Valley is located approximately 35 miles east of San Francisco and includes the towns of Pleasanton, Dublin and Livermore.

In 1970 the ALVHS proudly gained its first building located at the Alameda County Fairgrounds in the old Administration Building. The ALVHS quickly took possession of the old building and established the first museum in the area especially devoted to local history. Finally the ALVHS had a building in which they could preserve and display their many artifacts.

In 1984 the City of Pleasanton offered the vacant building at 603 Main Street to the ALVHS. This building, built in 1914 by funds donated by the Pleasanton's Women's Improvement Club, once housed the old Town Hall, the Police Department and the first free library in the city of Pleasanton. It was the perfect setting for an organization dedicated to preservation of the region's history.

Today, the ALVHS continues to successfully operate the museum and expand its mission and growth. Wishing to create an identity associated with its historic location, the society changed the name of the museum to Pleasanton's Museum on Main. The Board of Directors has a great vision for the museum's future. In 2008, the Board is developing the first Strategic Plan and Endowment.

The ALVHS is highly dependent on community support and derives its income from a variety of sources including membership dues, admission revenues, gift shop sales, special fundraising events, private personal and corporate donations, and reproduction fees. Pleasanton's Museum on Main offers rotating exhibits, a permanent exhibit, regularly scheduled lectures, in-house school presentations, and themed events. In 2008, the museum joined the national and international museum communities in celebrating Museum Month. Pleasanton's Museum on Main is a proud member of the American Association of Museums, California Association of Museums, and American Association for State and Local History.