Hoping that you're still using this e-mail address. I'm trying to locate any info that I can find on a "Nathaniel Greenough" that went to Maine. Records found indicate that a Nathaniel Greenough had an account at the trading post located at Ft. Pownall on the Penobscot River in current Stockton Springs. Account enries were made in 1773, and 1775. Your posting mentioned descent thru a Nathaniel Greenough that ended up in Bradford, Penobscot, Maine, which is on a line North from this lower area. Since Nathaniel was not found in any 1790 census along the Penobscot River, he may be the one who moved to Bradford.
My interests result from the fact that a child of Jeremiah Colson, of Bucksport, Maine, was named Greenough Colson. This is an extremely rare name for area, and might suggest a family connection. Jeremiah's parent was a Josiah Colson b. July 1746, and who had married an Elizabeth b. c1748. They were married c1765 possibly at Ft. Pownall. Elizabeth's nee surname is still unknown, and I am speculating on the possibility she was a Greenough, which would explain the later naming of her grandchild. The only Greenough in area at right timeframe was Nathaniel.
Any info you can provide on the Maine Greenough's would be appreciated. Thanks. Jack Colson