[zlwgfdtm] breadth of the U.S.

what is the longest east-west "line" of latitude across the lower-48 contiguous United States?  (not really a line because parallels other than the equator are not great circles.)  both endpoints in the U.S., but it may pass through Canada.

the easternmost point is in Maine; the westernmost is in Washington state.  however, lines of latitude get shorter as you get closer toward the poles (future post vajvywgs), so a line of latitude from Maine to Washington (actually to Oregon) might not be the longest east-west line.

this should be easy given the coordinates of the eastern and western borders.