Before becoming a lawyer, he unsuccessfully ran for state representative. He later won a seat in the state senate, serving from 1845 to 1848. Allen and Samuel Dexter established "Western Emigrant", Ann Arbor's first newspaper, which used to promote their anti-Mason views. Having become very influential in Ann Arbor, Allen moved to New York to better manage his financial affairs. He was unsuccessful in New York and by 1850, he had lost most of his wealth in real estate. Looking for ways to regain his fortune, he went west in 1850 to try his luck in the California Gold Rush. He died on March 11, 1851 near San Francisco.