The Public Land Commission, a former agency of the United States government, was created following the admission of California as a state in 1850 (part of the Compromise of 1850). The Commission's purpose was to determine the validity of prior Spanish and Mexican land grants in California.
California Senator William M. Gwin presented a bill that, when approved by the Senate and the House, became law on March 3, 1851. The Act established a three-member Board of Land Commissioners, to be appointed by the President for a three-year term (the period was twice extended by Congress, resulting in a five-year total term of service). Unless grantees presented evidence supporting their title within two years, the property would automatically pass into the public domain. This proviso has been viewed as being contrary to Articles VII and IX of the Treaty of Guadalupe Hidalgo, which guaranteed full protection of all property rights for Mexican citizens.
The land commission opened its sessions at San Francisco on January 2, 1852. It then consisted, by appointment of President Millard Fillmore, of Hiland Hall, Harry I. Thornton, and James Wilson as commissioners. In 1853 President Franklin Pierce changed the board by the appointment of Alpheus Felch, Thompson Campbell and R. Augustus Thompson as commissioners. Their commissions would, in accordance with the terms of the act, have expired in March, 1854; but previous to that time the operation of its provisions as to their power to act was extended for one year longer and afterward for another year. In 1854 Peter Lott was appointed commissioner in place of Campbell; and in 1855 S. B. Farwell was appointed commissioner in place of Lott. On March 3, 1856, five years after the passage of the original act, the board finally adjourned sine die.
Although the Commission eventually confirmed 604 of the 813 claims received, the cost of litigation forced most Californios to lose their property.
One of the more significant sets of claims was filed on February 19, 1853 on behalf of the Roman Catholic Church by Archbishop Joseph Sadoc Alemany, wherein he sought the return of all former mission lands in the State. Ownership of 1,051 acres (4.25 km2) (for all practical intents being the exact area of land occupied by the original mission buildings, cemeteries, and gardens) was subsequently conveyed to the Church, along with the Cañada de los Pinos (or College Rancho) in Santa Barbara County comprising 35,500 acres (144 km2), and La Laguna in San Luis Obispo County, consisting of 4,157 acres (16.82 km2).