After his mother died, the younger Allen and his father split their time between French Gulch and a Mill Creek ranch.
Allen graduated from local schools in Deer Lodge County and attended Helena Business College.
Upon earning his degree in 1891, Allen helped his father run the French Gulch mine.
He moved to Boston soon after the end of Edwin L. Norris's governorship and added real estate, fire insurance, banking, and railroads to his holdings.
In 1940, he contested the Republican primary for a seat on the United States House of Representatives, losing to Jeannette Rankin.