In Sacramento, Stanford started doing business with a few men of high status, including hardware dealers Huntington and Hopkins, and store owners, the Miller brothers. In doing this, he helped form the California's Republican Party. Stanford assisted presidents, such as Abraham Lincoln, in political events and became so interested in politics that he became the Republican Party's nominee for Governor. On January 10, 1862, Leland Stanford was sworn in. Before becoming governor, however, he was president of the Central Pacific Railroads of California, where he would later, in 1869, stop his work as a governor and continue his practices with Central Pacific Railroads of California.
In 1871, the Stanford couple decided to expand the square feet and height of the original 2 story, 4,000 square foot home to 19,000 square feet, adding 10 feet of brick and a story above and below the house. After the death of their only son, Leland Stanford Junior, born 1868 and died 1884, the couple decided to dedicate their business to helping children. After becoming a United States Senator, Stanford died in June 1893, leaving the estate to Jane. After her death in 1900, the residence was given to the Catholic Bishop of Sacramento, where it would be turned into an orphanage managed by nuns. The house also transformed into a settlement house and later, a high school for girls.
The house was named a state historic landmark in 1957. In 1991, Peter McCuen, created the Leland Stanford Mansion Foundation to restore the mansion and have it available for tours and visitors. It now resembles the original house built in the Victorian Era.