The first 16 miles of the Lower Potomac River Marathon course are completely flat mostly along the water. There is a 6 miles stretch from miles 16 to approximately 23 that travels inland and has some small gently rolling hills. The course then returns to the coast for a flat finish.
Typical race day weather is cool and this, coupled with the fast course can lead to PRs and Boston Marathon qualifying times.
See what splits you need to run for hundreds of different marathons - adjusted for the specific terrain of each marathon, your goal time and pacing strategies.