Of the more than 400 sites in Los Angeles County that have been listed on the National Register, fewer than ten received the distinction prior to the Ygnacio Palomares Adobe.

[3] In 1837, Mexican Governor Juan Bautista Alvarado granted the land to Ygnacio Palomares and Ricardo Vejar, both Californio sons of New Spain natives.

[4] Palomares initially lived in "La Casa Primera", an earlier adobe which is also operated by the Historical Society of Pomona Valley.

[4] The Palomares Adobe was used for a time as an overnight stagecoach stop at the midway point between Los Angeles and San Bernardino.

[6] The Palomares home was reportedly "the heart of the rancho," with its doors open to travelers and a store that provided goods to settlers.

[2] The large living room served for many years as a meeting place and a chapel where padres from the San Gabriel Mission would travel once a month to say mass.

[5] Ygnacio Palomares and his wife operated the land as a sheep and cattle ranch, grew their own crops, and raised five children at the adobe.

[2][11] Charles Gibbs Adams oversaw the landscaping restoration, with tree plantings, shrubs and rosebushes located close to where they had been in the mid-19th century.

"[7] Two years later, the Los Angeles Times reported: "The structure has become famous throughout the nation as a permanent museum housing many relics and equipment of the early Spanish days in California.

In December 1939, Porfiero R. Palomares (c. 1871–1942), who was born in the adobe and was the grandson of Don Ygnacio, moved into the restored structure as caretaker with his wife and daughter.