Hagerman was born in Milwaukee, Wisconsin to industrialist J. J. Hagerman. He worked at several low-level jobs in his father's businesses during his teen and college years, including his father's ranch near Roswell, New Mexico. He received his law degree from Cornell Law School in 1894, and became a member of the Kappa Alpha Society. After passing the bar, he practiced law in Colorado, where he had moved in order to be closer to his father's mining interests. Hagerman never married, and had no children.
Start of career
In 1898 became Secretary to the United States Embassy in Russia, a position he held until 1901. Working closely with Ambassador Ethan A. Hitchcock, Hagerman impressed his boss with his abilities and his eagerness to stem waste and corruption. Hitchcock was recalled to Washington in 1899 to serve as Secretary of the Interior. Hagerman resumed practicing law and taking part in his father's New Mexico ranching interests. In 1903 he was appointed to New Mexico's Board of Managers for the Louisiana Purchase Exposition, also known as the St. Louis World's Fair. He was an alternate delegate to the 1904 Republican National Convention.
In 1906 President Theodore Roosevelt was attempting to curb the political corruption which was rampant in New Mexico. Remembering Hagerman's abilities from his time in Russia, and aware of Hagerman's ties to New Mexico, Hitchcock suggested him as a candidate for Governor. Roosevelt appointed Hagerman on January 10, 1906. As Governor, Hagerman was strongly opposed by the political bosses of New Mexico. They waged a campaign of negative publicity against him, and succeeded in blocking most of his proposed reforms. The leaders of New Mexico's political establishment submitted a long list of spurious charges against Hagerman to Roosevelt. Roosevelt ultimately sided with the New Mexico establishment and asked Hagerman to resign. Roosevelt was inundated with pro-Hagerman letters and telegrams from the citizens of New Mexico, but did not reconsider his decision. Hagerman left office on May 3, 1907.
Later career
After leaving office Hagerman returned to the practice of law in Santa Fe and Roswell. From 1923 to 1931 he served as federal commissioner to the Navajo nation, initially appointed by Albert Fall, a New Mexican who was serving as Secretary of the Interior.
