Here is where the title of "oldest public library in the US" starts getting into semantics. One library claims the title of oldest building, and another claims oldest building constructed to be a library, and so on. Some libraries started out as subscription libraries while others were open to the public from the beginning. Another distinction was whether books could be removed from the library or only used within the building. Following are some short descriptions of some very old libraries in the US.

The Sturgis library claims the title of oldest building being used for a library in the US. Located in Cape Cod, Massachusetts, the building was constructed in 1644 originally to serve as a home. This library building appears to have been added on to a number of times. The library itself was established in 1863. 

Also vying for the title of oldest library in the US is the Redwood Library in Newport, Rhode Island. It occupies the oldest building constructed to be a library. The Redwood started out as a subscription library and dates back to 1747. 

The Darby Free Library in Darby, Connecticut (established in 1743) calls itself "the nation's oldest public library in continuous service."

Scofield Library in Salisbury, Connecticut claims a "first," as well. According to their website they started out in 1771 as a subscription library. The original benefactor was a loyalist so he left for England when the Revolutionary War broke out. Citizens continued to purchase books for the library until  1810, when the city voted to purchase books for the library. In this way, Scofield became the first "publicly funded library."

To honor their namesake, the town of Franklin, Massachusetts asked Benjamin Franklin to donate a bell. He decided to donate "sense" instead of "sound" and in 1790 he donated 116 books to Franklin. City leaders voted to allow the public to access the books, so they claim to be the oldest public library in the US.

The Library Company of Burlington, New Jersey still operates under a business charter signed by King George II in 1757. Several members of this subscription library worked with Benjamin Franklin when he started the Philadelphia Library Company.

Boston Public Library (BPL) was established in 1848 and considers itself the first free municipal library. City leaders were reluctant to commit to a public library. However, when John J. Astor died, he left money for New York City to establish a library. The long-standing cultural competition between the two cities came to a head, and Boston opened their library two years before New York. Boston Public Library opened the first branch library in the US in 1870 and now supports 26 branches throughout Boston.

In 1638, John Harvard donated a portion of his estate as well as 400 books to a college in Boston called New College, which was later renamed after Harvard. As the school grew, different library buildings were used. In 1912, the grieving mother of a Harvard graduate who had perished on the Titanic endowed Widener Library with the instruction that the exterior was not to be altered. As Harvard outgrew this building, the library moved underground, and now boasts two floors above ground and five underground levels. Harvard University Library is not open to the public.

To sum up the oldest library debate: New Hampshire, Rhode Island, New Jersey, Pennsylvania, Connecticut and several Massachusetts libraries each claim to be the oldest library in the United States. They all have their own reasoning, but regardless of who can claim the record, libraries have been an important part of American communities for a long time.