It was added to the National Register of Historic Places in 1974, making it among the first 25 sites in Los Angeles County to be so designated (there are now more than 450).

[2][3][4][5][self-published source] He moved to Spadra (now part of Pomona) in 1862 and began engaging in sheep herding and cattle raising.

"[8] The Times noted that Phillips was worth "not a dollar less than $3,000,000" and stated that, in addition to his land holdings in Los Angeles, he had a ranch that produced wool, honey and wheat.

"[11] Another writer noted that it "looks as if it had been lifted bodily from the tree-lined street of a midwestern county seat," the "kind of house the banker of such a town would build for himself.

"[15] The property on which the Phillips Mansion was built is part of the 22,000 acre Rancho San Jose land grant awarded in 1837 by Gov.

Even before the construction of the Phillips Mansion, it was said that "the cluster of buildings by San Jose Creek at the foot of the Spadra Hills" was the center of life on the rancho.

[16] In January 1874, the Southern Pacific Railroad completed a rail line from Los Angeles to Spadra,[9] spurring interest in land development in the area.

[10] However, Phillips preferred Spadra to Pomona,[10] and retained 2,241 acres (9.07 km2) surrounding his mansion, which he operated as a cattle and sheep ranch.

[10][20] Phillips also became postmaster for the Spadra area,[13] and the mansion became both the post office and a center of social activities for the scattered settlers of the Pomona Valley in the late 19th century.

[6] His widow Esther lived at the mansion until 1916,[13] and it remained in the Phillips family until 1931, when their grandson, Cecil George, sold it to Paul T. Boyle of Los Angeles.

In 1966, the mansion was heavily vandalized,[17] and plans were announced to sell the property to a buyer who intended to build a paint factory on the site.

[13][14] Pomona architect Amos W. Randall was in charge of the renovation master plan, and the restored mansion was opened for its first public viewings in 1978.