Vacaville is located in Solano County, California midway on Interstate 80 between Fairfield and Dixon. According to Vacaville, The Heritage of a California Community (1978, Vacaville City Council):
“Vaca Valley is the southern part of a long trough extending northward to Putah Creek, with the English Hills rising to the east and the Vaca Mountains to the west. Vaca Valley itself runs nine miles northward and includes Ulatis Creek on the east and Alamo Creek on the west. After a low divide at its northernmost point, it shares the interrange trough with Pleasants Valley…A third basin, lying to the west and south of Vaca Valley is tiny Laguna Valley. These three valleys have been closely associated in the history of Vacaville since the 1850s and they also had much in common in the history of the region before that time.”
Currently, Vacaville is also the postal code area for old settlements of Elmira and Bucktown (with Tremont, Maine Prairie, and Silveyville being closer to the City of Dixon).
In the early days, Vacaville was known nationwide for its production of fruit, with 21,000 gallons of wine being produced in 1865. With a fifth of the population being Chinese laborers in 1880, crops produced with their help included cherries, yams, flax, hemp, tobacco, rice, olives, peaches, figs, pomegranates, walnuts, apricots, dates, almonds, oranges, and lemons among others.
Vacaville - Pleasants Valley 
Later, the city became a hub for Travis Air Force Base and State Prison personnel, as well as many employees working in the greater Bay Area and Sacramento. Bio-tech firms and great shopping destinations ultimately developed within the city. Vacaville is the home to our own Solano County Genealogical Society with our research library located upstairs in the Old Town Hall at 618 East Main Street, which was built in 1907. The town provided a lot and $1,500 and the County of Solano chipped in $3,500 to replace the old wooden jail that had mysteriously fallen down. The steel and concrete two story structure included the fire department and jail on the first floor with hose carts in front and a drunk tank in the back. Upstairs held two offices for the justice of the peace and the city clerk, as well as a chamber for the trustees. Above it all was the tower containing the fire bell. It is listed on the National Register of Historic Places.
For a brief history of the City of Vacaville, follow this link to the city’s official website.
A designated section of the City’s website for the Fire Department also has a brief history of that department which details its history since its inception in 1895. This history begins with this quote: “The early morning calm in the village of Vacaville was shattered by a powerful earthquake on April 19, 1892. Estimated to be 6.4 on the Richter scale, it would lead to the incorporation of Vacaville as a town in just three months.”
Old Town Hall in Vacaville - Location of the Solano County Genealogical Society Research Library
Fifty years prior to that incorporation, Juan Manuel Vaca arrived from New Mexico and owned a large rancho called “Los Putos” in 1842. It had been inhabited by the Southern Patwin Indians of the Wintun culture group, however, a smallpox epidemic between 1837 and 1839 left less than 100 Patwins in the area. In 1851, Juan Manuel Vaca sold a nine square mile plot of that land to rancher William McDaniel. As part of the land transfer, McDaniel would then use one square mile to become the town of “Vacaville.” The Mapa de Villa de Vacaville, Estado de California was filed with Solano County officials on December 13, 1851. Vaca’s contemporary, Juan Felipe Pena, probably reached the area as early as December 1841 and settled in the Laguna Valley. General Mariano Guadalupe Vallejo once stated that he suggested the area to the Vacas and Peñas. To learn more about the Peña Adobe shown below after its 1967 renovation, visit the Peña Adobe Historical Society website.

Peña Adobe 

Additional Links:
The Vacaville Heritage Council, established in 1968, is a non-profit historical archives and research organization specializing in local Solano County History. Located on the main floor of the Old Town Hall at 618 East Main Street, Vacaville, the Council is open Tuesdays and Thursdays from 9:00 AM to 1:00 PM or by appointment for research and tours.
Visit Vacaville website for tourists, visitors, and hometown fun