It is certainly possible for someone in a manual wheelchair to travel the streets of Boston without taking any form of public transportation; however it all depends on one’s stamina and endurance because there are slight inclines and well, using a manual wheelchair regardless takes some muscle.
However, the subway in Boston, known as “The T,” is a great system if you want or need to take a break. It’s important to plan out your journey before hand though because not every stop is wheelchair accessible; many are but pick up a public transportation map at any station or information booth found around the city.
For those who are disabled there is a reduced fare and you should ask a ticket attendant for help if you cannot find this discounted option. For the stations that are accessible there are usually elevators and special ticket gates for your comfort. Furthermore, some of the smaller stations around the city that are accessible might have ramps, like the one shown below close to the Museum of Fine Art, Boston.