The Internal Revenue Act of 1 July 1862 was intended to provide revenue to support the government and help pay the national debt. The 1862 to 1866 tax assessment lists for Maine are at the National Archives—New England Region and at the Family History Library. See:
United States. Commissioner of Internal Revenue. ''Internal Revenue Assessment Lists for Maine, 1862- 1866''. Washington, D.C.: National Archives and Records Service, 1970. (
FHL [http://www.familysearch.org/eng/library/fhlcatalog/supermainframeset.asp?display=titlefilmnotes&columns=*%2C0%2C0&titleno=577884&disp=Internal+revenue+assessment+lists+for+Ma++ films 1534403-17].) This source lists name of person taxed and residence. It may also list occupation and type of tax.