He was at the front of the Pike's Peak Gold Rush, arriving in Denver of the Kansas Territory (now the state of Colorado) in October 1858.
He was a founder of a company that diverted water from the South Platte River through irrigation ditches.
[3] Allen enlisted in the United States Army on March 25, 1844, at Fort Moultrie (Sullivan's Island, South Carolina), he served in Puebla City, Mexico.
He was discharged as a private November 1, 1847 due to a disability,[2] but he had been identified at times as Major and then Colonel Henry Allen.
Attendees included Charles Blake, George Lehow, William M. Slaughter, and Dr. Russell.
[5] He purchased a number of lots in Auraria and in July 1859, his wife Susan and their grown daughters moved there.
[5] He held a meeting to consider forming the State of Jefferson and was the delegate from Auraria to the first Constitutional Convention.
[5] D.C. Oakes and William N. Byers both wrote guides to the Pike's Peak region that some believed made promises about quick success.
[7] Allen wrote of fellow immigrants to the Council Bluffs Bugle on May 18, 1859: A great many calculated that they could make a fortune in a few days, and when they came out, finding that it was going to take work to do it — they were in a wild county — no female society — no provisions but wild game — they began to think of their happy home in the States, and commenced singing 'Do they miss me at home' and at once started off to see if they were missed.He was one of the founders of the Colorado Hydraulic Company on February 2, 1860.
[5] The Allens lived in mining towns in Colorado, Idaho, and Montana, with varying degrees of success.
[1][b] At the time, Allen was a member of the Los Angeles Lodge F.[14] Susan returned to Montana and lived with her daughter.