In his blog for The Atlantic magazine, James Fallows claimed that Eastport, ME was the easternmost point in the US. A writer commented that no, the easternmost point in the US was somewhere in Alaska, as Alaska crosses the 180th meridian. Another correspondent (me) wrote that this was silly - that the easternmost point of a landmass is the extreme point of the landmass that can be reached by traveling in an easterly direction, or more precisely, the last point on the country found by sweeping a line of longitude in an easterly direction. (This is more complicated for countries that don't have contiguous territory, but for now let's assume the territory is contiguous (and yes, I know that Alaska borders Canada and not another US state)).
Is there any convention in the geography community that establishes the meaning of "easternmost", preferably one that can be cited?