The Boston Public Library is a municipal public library system in Boston, Massachusetts, United States. It was the first publicly supported municipal library in the United States, the first large library open to the public in the United States, and the first public library to allow people to borrow books and other materials and take them home to read and use. The Boston Public Library is also the library of last recourse of the Commonwealth of Massachusetts; all adult residents of the state are entitled to borrowing and research privileges, and the library receives state funding. According to its website, the Boston Public Library contains 6.1 million books, making it one of the largest public libraries in the nation.