(Francis March) Hatch started practice with the law firm of Castle & Hatch in early 1878. His partner was William Richards Castle, a scion of the missionary family first sent to Hawaii in 1837 by the American Board of Commissioners for Foreign Missions. Castle, three years older than Hatch, had been admitted to the Hawaii Bar in 1876, and had practiced in New York City, returning to Hawaii to become Attorney General in 1876. The young lawyers established their law office on Kaahumanu Street, opposite the old Post Office building on Merchant Street, which is still there, but Kaahumanu Street was closed to accommodate a municipal parking garage. Nearby were the two or three story offices of the sugar factors, like H. Hackfeld & Co. and Castle & Cooke, a dry goods store, a harness maker, the Hawaiian Gazette Building, ship chandlers and warehouses.