Leo Poirier was born in Berlin, New Hampshire in 1891 to James Poirier and Lemina (LaForge) Poirier. In 1902, his family moved to Van Buren because his father had a job constructing the mill for the St. John Lumber Company of Keegan, Maine. Leo Poirier worked shipping lumber from Van Buren to Boston and then taught school in Van Buren. He later worked in the woods as a scaler and river drives as well as in a saw mill.