Harrison was Governor-General of the Philippines from 1913 to 1921 and advocated for and oversaw the process of Filipinization, or the transfer of authority to Filipinos in the United States territory's Insular Government to better prepare for independence. He was governor-general during the passages of the Philippine Autonomy Act, otherwise known as the Jones Act, which converted the partially elected Philippine Legislature with the appointed Philippine Commission as the upper house and the elected Philippine Assembly as the lower house, to a fully elected Philippine Legislature with the Philippine Senate replacing the now-dissolved Philippine Commission and the Philippine Assembly renamed the House of Representatives of the Philippines.