JUDY WOODRUFF:

About four million people visit their local library every day in the U.S. Some have nowhere else to go. The American Library Association can't put a number on how many homeless people are using their facilities as shelter, but many cities are struggling to address the problem.

In San Francisco, where more than 7,000 people are homeless, the city decided to take an unusual approach, placing a social worker inside the library.

The NewsHour's Cat Wise has our report.