We live in northern RI and this is our route:
146 to i-90 to I-84 to i-81. I-81 south to Harrisburg. At Harrisburg, we take the beltway (322 and I-83) clockwise to route 15, which we take down into Maryland to I-270. We take i-270 to I-495 (Washington Beltway) and connect to I-95. We take i-95 into Florida although we do take the I-295 bypasses around Richmond, VA and Jacksonville, FL.
Others go farther south on I-81 but i don't want to try the extreme hills between Blacksburg, VA and the North Carolina boarder. I am sure that others have many variations of the route.
good luck.
--jack