I was searching around today and I found two very interesting maps of Maine. I love maps almost as much as Bilbo Baggins I expect, and old ones are truly fascinating. These two are from 1831 and 1845, and I believe both can be found in the map collection at USM.
The older of the two was drawn and published by David H. Burr. It shows the borders of the counties of Maine as of 1831 - northern Maine was divided between Washington County (yellow), Penobscot County (green), and Somerset County (pink) - as well as various versions of the border between Maine and New Brunswick. The various versions of the border is what is interesting, because that border was hotly contested from 1783 until 1842. There are no less than three border lines.
The later map, made in 1845 shows the border line that was decided upon, and the one that has remained so until the present.
From http://www.mainehistory.info/history.html I found this brief account of that northern border dispute, a matter I very much want to look into at more detail.
"The precise boundary line between Maine and New Brunswick remained a matter of often-heated argument for years after the close of the Revolutionary War.
The dispute festered and smoldered until 1839, when it threatened to erupt into open warfare. The Maine Legislature that year raised funds to support a military force of 10,000 to protect the state's border claims at Madawaska.
Several hundred British regulars were dispatched to the scene from Quebec. At this point the U.S. Congress entered the picture, approving $10 million for military expenses should war break out.
Nearly 50,000 troops were readied for action, and Major General Winfield Scott was dispatched to the scene. Scott managed to work out a temporary agreement between the two parties before the so-called "War of the Aroostook" reached the point of bloodshed.
The Webster-Ashburton Treaty, hammered out in 1842 by U.S. Secretary of State Daniel Webster and English special minister Lord Ashburton, finally settled the question of where Maine's northeast boundary lay. "