In 1911, Hartley's eldest son Jack and brother-in-law William Jay Stevens developed the plot into one of San Diego's early residential and commercial districts. After first establishing Stevens & Hartley, North Park's first real estate firm, in 1905, Jack and William built North Park's first "high rise" commercial building, the Stevens building, on the northwest corner of 30th Street and University Avenue (today's "Western Dental" building) in 1912. "Thirtieth & University" became North Park's symbolic place name, and within 10 years, this became the heart of the community.