New Jersey legislature
In 1905, Colgate entered politics as a progressive Republican. In 1905, he was elected to represent Essex County in the New Jersey General Assembly, serving in the 130th Assembly. He was re-elected in 1907 and 1908, serving in the 132nd and 133rd assemblies. In 1911, Colgate was elected to represent Essex in the New Jersey Senate. He was re-elected to a second term in 1914. He served in the 136th through 140th legislatures.
In the legislature, Colgate was remarkably active. He introduced numerous bills to advance progressive and humanitarian causes, including proposals to exempt public playgrounds from accident claims, ban drunk and reckless driving, extend workers' compensation benefits to cover occupational diseases, establish a minimum wage commission, cap the criminal sentencing of children under sixteen, protect fish and game, control mosquitos, mediate labor disputes, reform the child welfare system, permit women police officers, expand public record-keeping, require licensing for dance halls, and expand public funding for the care of tuberculosis patients and the developmentally disabled. He also promoted legislation for the government study of blindness and mental retardation.
In the field of political reform, Colgate also successfully supported laws establishing a direct primary, reforming child labor, establishing the Civil Service Commission and Public Utility Commission, a widows' pension act, and a long line of other successful progressive measures.
