Changes since 1855 in reported section-line lengths and positions of survey monuments that span the San Andreas fault (SAF) were used to measure displacement interpreted to be from the 1857 Fort Tejon earthquake in south-central California. In 1855–1856 James E. Freeman established township and range lines across the SAF between Rancho Cholame and the northern Carrizo Plain. At least 26 1-mile sections lines spanned the SAF in the area between present-day California Highways 46 and 58. Each section line was marked by monuments at the midpoint and endpoints. Section lines across portions of the SAF were resurveyed in 1893 by J. M. Gore. We projected changes in line length onto the fault zone to measure displacement.