Depending on what route you take it is anywhere from 386km - 465km
Its between 342 to 453 kms based on the route you take.
Niagara falls is in NY.
Take QEW WEST to Niagara Falls.
10 or 20 days
You can get a plane that will take you from Washington DC to Niagara Falls Ontario. It might not be a direct flight, you might have to change planes, but, there are flights that leave from Arlington, Virginia to Niagara Falls.
7 hours
Check Mapquest.com
The distance between Boston and Niagara Falls is about 410 miles. Should take 7 hours or so to get there from Mass.
It depends on which route you take really but the 3 quickest routes are 1,330 miles, 1,340 miles, and 1,370 miles. Time is 22-23 hours.
A little over 7 hours
The distance between Niagara falls and Keeseville ny is 372 miles and will take about 6 hours 44 minutes to drive.