El Sobrante was called “Oak Grove” by industrial concerns in 1887 when the California and Nevada Railroad put a spur into the area for the purpose of carrying lumber cut from the hills. Then the name Sobrante was applied, with the addition of the Spanish definite article “El” coinciding with the opening of the first post office in 1941.
By the early 20th century, Rancho El Sobrante had been reduced to a number of smaller ranches, generally following a dirt road along San Pablo Creek. Many of these ranches were further subdivided. As roads were paved and homes were constructed, El Sobrante changed from a rural to a semi-rural community