There are many published biographies of Maine residents at the Maine Historical Society. The Maine State Library also collects biographical materials.
One of the few representative biographical encyclopedias about Maine at the Family History Library is:
Herdon, Richard, et al. Men of Progress: Biographical Sketches and Portraits of Leaders in Business and Professional Life in and of the State of Maine. Boston, Massachusetts: New England Magazine, 1897. (Family History Library book 974.1 D3m; film 1000057 item 2).