In the 1850s and 1860s, businessmen and political leaders such as Andrés Pico, Sanford Lyon, Henry Clay Wiley, Darius Towsley, and Christopher Leaming came to the Santa Clarita Valley for its oil reserves. On September 26, 1876, the town of Mentryville was founded by French immigrant Charles Alexander Mentry near present-day Stevenson Ranch. Mentryville's Pico Number 4 oil well was the first commercially successful oil well in the western United States. Oil from Mentryville was refined at Pioneer Oil Refinery in Newhall, the first viable oil refinery in the state. Many of these oil pioneers have lent their names to streets in the valley, such as Pico Canyon Road, Lyons Avenue, Wiley Canyon Road, and Towsley Canyon Road.