Mt. Diablo

What does Mt. Diablo in the Contra Costa County of Northern California, have to do with Lemoore? Several articles on our website mention either a township, a section, or a range and that is why the existence of Mt. Diablo is important. Lemoore was established in Section 3 at the north edge of Township 19 South, Range 20 East, Mt. Diablo Meridian. Today this would be Hanford-Armona Road to the north, Kent Avenue to the south, 16th Avenue to the east and 22nd Avenue to the west.

After the Mexican-American war ended in 1848 the “Ranchos”, or private land holdings that had been established during Spanish and Mexican rule, were honored under the Treaty of Guadelupe Hidalgo with Mexico by the United States Government. California was admitted to the Union shortly after the end of the war in 1850.

These ranchos covered almost 9 million acres, or 14,000 square miles along coastal areas, and in the San Joaquin and Sacramento Valleys. The U. S. Government needed to define these properties so United States Deputy Surveyors were assigned the task of surveying the rancho boundaries. More than 30 government survey parties were deployed during the 1850s.

While the surveying of the rancho boundaries was being done, the government also began plans to subdivide the federal lands in the territory in accordance with the United States Public Land Survey System (USPLSS). The procedure for surveys under this system was to establish a starting point. This starting point is called the “initial point”1, which is the intersection of true east/west and north/south direction lines.

Originally California was to have only one initial point, but due to the size of California and ruggedness of the terrain in many areas, the Surveyor General decided three initial points were needed. Mt. Diablo, in Contra Costa County, was the first of these points established in 1851. In 1852, the second point was established on San Bernardino Mountain in San Bernardino County and in 1853 the third point was established on Mt. Pierce in Humbolt County.

In July 1851, Col. Leander Ransom, General Land Office Deputy Surveyor, was under instructions from the Surveyor General for California to establish the initial point on Mount Diablo’s Summit.

In oppressive summer heat that year, he labored through dense brush up the steep terrain to get to the top of the mountain. There he chiseled a hole in solid rock on the highest point, and erected a pole to be used as a sight to establish monuments on the base and meridian lines. The Meridian line is basically the north/south line and the Base Line is the east/west line. Townships are numbered North and South from the Base Line. Ranges are east and west from the Principal Meridian.

Ransom then went due south 12 miles and set additional monuments to establish the meridian. He continued setting monuments due east, due north, and due west of the initial point on the summit of the mountain, thereby establishing the Mount Diablo Base and Meridian lines. Ransom began on July 17, 1851, and completed his survey on August 31, 1851.

Once the base and meridian lines were established, public lands were then divided into thirty six square mile blocks called survey townships. The township blocks were further subdivided into thirty six sections, with each section being one square mile, or approximately 640 acres. Sections can sometimes be recognizes in rural areas where they are delineated by county roads and fence lines. Sections can be further divided into quarters, 160 acres, and eighths, 40 acres.

Today a museum sets atop Mt. Diablo, where on a clear day more land can be seen than anywhere else in the United States. The summit of Mount Diablo is inside the Mount Diablo Summit Building. An exposed piece of rock, which is the summit of Mount Diablo (elevation 3,849 feet) is left unpaved for visitors to stand on.

For more information visit these other websites:

  1. By definition an Initial Point is singular, finite, unique, one of a kind. An Initial Point normally establishes the base and meridian lines as defined by the United States Rectangular System for the orderly subdivision of land for a defined region. It officially marks the intersection of two lines extending out to the north, south, east and west as far as is necessary to reach the boundary of the next base and meridian. []