The two story museum building was the annex to the original 4 story stone grist mill, 3 stories stone & one story frame. The annex was used for grain and feed storage, having been built in 1880, when William Rogers was in charge of the mill. Then the mill was the center of an ice making business, the Los Gatos Ice Co. used the steam power of the mill to produce ice for residents of Los Gatos in the late 1880'/early 1890's. The enterprise became electrified, becoming the Los Gatos Ice & Power Co. Then later the Los Gatos Ice, Gas & Electric Co. Today it is the Forbes Mill Museum of Reginal History at 75 church St. across from the Los Gatos Civic Center.

Scottish born James Alexander Forbes was schooled in Argentina before coming to the bay area of California in 1831, a young man of 27 years. He spent the first 18 years in California employed by the Santa Clara Mission, the San Jose Pueblo, and Hudson Bay Co. He invested early in the New Almaden Quicksilver Mine. It was during this time, about 1850, that he noticed that most of the flour for baking bread was imported from Chile at an exorbitant cost. He decided that a flour mill was needed locally, so he bought 2,000 acres that included a good mill site, along the Los Gatos Creek from the Rinconada de Los Gatos Rancho.

In 1853, after getting enough money to start, he began to build the 4 story mill, sometimes called the Santa Rosa Flour Mill, using stones quarried from Los Gatos Creek downstream of the mill seat. A dam was constructed upstream and a headrace that included an 880' wooden flume brought water from the dam to the mill. The milling equipment didn't arrive til late 1855; Then, actual milling started in Dec. 1855.

Forbes lost the mill, for a variety of reasons, to the note-holder G. Touchard in 1857. No one seemed to be able to make a success of the venture until William H. Rogers bought the mill and 60 acres in 1866. Rogers, a New Yorker, learned milling while working in the Detroit City flour Mill. In California in 1853, he did some gold mining around Placerville; then, along with a few others, he built the Mountain Flour mills close to Placerville, running it until 1860.

Soon after buying the Forbes MIll, Rogers raised the head to 65', installed 2 turbines to replace the 20'waterwheel, and made other upgrades. The same year as the annex was built, a gradual reduction grinding system was installed, utilizing the process of reworking (grinding) the tailings three or four times to greatly increase the production, with less waste, to 200 barrels/day. A woolen mill, built in 1869 by the same owners, the Los Gatos Manufacturing Co., was located about 100 yards west of the mill (on the other side of Ca 17 today). This mill burned in 1872, not to be rebuilt.