High Quality Content by WIKIPEDIA articles! The Phillips Mansion is a Second Empire style historic house in Pomona, Los Angeles County, California. It was built in 1875 by Louis Phillips, who by the 1890s had become the wealthiest man in Los Angeles County. Situated along the Butterfield Stage route, the Phillips Mansion became a center of community activity in the Pomona and Spadra area. 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.)