If you want a fast, flat race this one is it!
Baystate runs along both sides of the Merrimack river in Lowell. It's not the prettiest course, but it may be the easiest (if any half marathon/marathon course can be 'easy'). The most elevation you'll get is going over the railroad bridge.

Another great part of this course is that it's very spectator-friendly. People can get to the course at any number of spots, including the Rourke bridge which allows for multiple spottings of their runners.

Both the half and the full are double-loop courses.

Nice long sleeved shirts and medals.