What is half way mark to Columbia Md from Morrstown Tn. what exit do I get off where there are resturants? -

It looks like this trip will take you on I-81 north until exit 300, and then east on I-66 to I-495 N(the Washington, DC beltway), then I-95 north to Columbia. The whole trip should take you about 7.5 hours, unless the end of your trip coincides with rush hour in Washington DC; if you reach the beltway at that hour, and then it could take you considerably longer because the DC beltway can have horrific traffic.The halfway mark would probably be somewhere on I-81, since you are on that road for quite a stretch. Lexington, VA is about 4 hours into your drive, just off I-81 on the exit marked E Midland Trail/US-60W . If you take US-60W far enough, you will reach the edge of the campus of Washington and Lee University and you will find various restaurants there.