While hundreds of the library buildings have been adapted for use as museums, community centers, office buildings, residences, or other uses, more than half of those in the United States still serve their communities as libraries over a century after their construction. Many are located in what are now middle- to low-income neighborhoods. For example, Carnegie libraries still form the nucleus of the New York Public Library system in New York City, with 31 of the original 39 buildings still in operation. Also, the main library and eighteen branches of the Pittsburgh public library system are Carnegie libraries. The public library system there is named the Carnegie Library of Pittsburgh.