A graduate of the University of Minnesota College of Law, Harold James Richardson practiced law with his brother in Rochester from 1900 to 1912, when he moved to St. Paul to become an associate of former Chief Justice Charles M. Start and future Ramsey County District Court Judge Kenneth G. Brill. In 1931 he became a member of the firm Clapp, Richardson, Elmquist, Briggs and Macartney. It grew over the decades through mergers and is today known as Briggs & Morgan.
He died on March 4, 1952, aged eighty. At memorial services for the Ramsey County Bar Association that year, his former partners recalled him:
"He was a gentle spirit given to tempering all judgments with kindness and mercy. The firmness he displayed developed naturally from the soundness and justice of his position. In argument a pointed question from him was often an adequate brief in reply.
"A law partnership is a close relationship, testing the capacity for tolerance, sympathy and forbearance. It calls for a fair appraisal of abilities and contributions to a common effort. It requisitions maximum mutual helpfulness and the highest order of friendship.
"Harold was a real partner.
"He and his associates maintained to the last that mutual respect and feeling for each other which rest upon the broader humanities."