Hotels in Massachusetts you can book at 18
Every Massachusetts city covered here fits a different kind of trip. At 18 the thing that can stop you is a hotel that will not check in anyone under 21, and these cities do have 18+ hotels. You are booking one city, not the whole state, so look below and see which one fits your trip.
10 hotels
Boston
Hotel list coming soon
Cambridge
Hotel list coming soon
Springfield
In Massachusetts the choice is two miles or ninety
Boston and Cambridge sit about two miles apart, so choosing between them is a question about your trip rather than about the map. Springfield is roughly ninety road miles west of Boston, far enough to work as its own destination and not a nearby alternative, so a trip whose reason is in Springfield books in Springfield. Finding hotels where you can check in at 18 narrows the field, and it does not tell you which city you belong in.
Two miles apart, two different reasons to be there
The Massachusetts State House is at the western edge of Boston Common, its golden dome visible on Beacon Hill, and it holds the State Senate, the House, and the Governor's Office. Boston is the capital of the Commonwealth, so if the State House itself is where you need to be, Boston is fixed before you look at a single room.
Cambridge is not the overflow option for the city two miles away. It has the region's largest inventory of hotel rooms outside Boston, and it calls itself the City of Squares, made up of nine neighborhoods. MIT's address is 77 Massachusetts Avenue in Cambridge, so a trip built around that campus belongs on the Cambridge side of the two miles.
Ninety miles west changes what the trip is about
Springfield is the birthplace of basketball, and the Naismith Basketball Hall of Fame is at 1000 Hall of Fame Avenue in the city. Springfield also uses City of Firsts as its own label. At roughly ninety road miles west of Boston, Springfield is outside the two-mile question entirely, so a trip that exists because of the Hall of Fame is a trip that books in Springfield.
Landing in Massachusetts leaves the eastern choice open
Logan International Airport is in East Boston, roughly three miles from downtown Boston and across Boston Harbor from it. From Cambridge the same airport is about eight miles out. The two figures are not equal, and the shorter one belongs to Boston.
Neither figure decides the city. The same airport serves Boston and Cambridge, so an arrival at Logan does not pick which of the two you stay in, and the fixed destination that got you on the plane still does. You do not have to book the city your flight lands in.