My husband and I would like to travel from Washington DC to Niagara Falls then on to Boston as part of a larger trip we are planning for next year.
Would you recommend driving or the train?
How long would each leg of the trip take?
How long would you spend in each place?

THis is a very long trip -- WashDC to Niagara is probably 9-10 hrs., as is Niagara to Boston. The train will take still longer.

You could break up the DC-Buffalo trip by stopping to see "Falling Water" (Frank Lloyd Wright's house built over a waterfall), or take a slight detour and see something of Pittsburgh.

Spend 1-1 1/12 days at Niagara, stop in the Berkshires at a B&B to break up the next leg, then spend 3-7 days in the Boston area.

PS: Interstate 81 through Penn. between DC and Buffalo runs along the tops of some of the Allegheny Mtns. and is given to lousy weather and/or fog, which can add more time to the whole trip.

Each leg is about 475 miles. Drive time should be between 7 and 8 hours. 2 days in Niagara FAlls, a minimum of two days in Washington, DC. I would do the trip by car,

I'd recommend you fly Southwest from BWI to Buffalo/NFalls ($39 right now) then Amtrak Lakeshore Limited to Boston, then either Amtrak to DC or again take Southwest from Providence or Manchester NH.

I like the train, but you'd be traveling over the same route (Albany/Buffalo) twice, and between DC/NY twice too with trip entirely by Amtrak ... unless you went from DC - Chicago-Buffalo-Boston.

Southwest's fares really win hands down over Amtraks, but the trip from Buffalo to Boston should be quite enjoyable. (remove x from my eddress to write me)