Students initiated a major demonstration in 1968 over two main issues. The first was Columbia's proposed gymnasium in neighboring Morningside Park, perceived as a segregated facility, with limited access by the black residents of neighboring Harlem. A second issue was the Columbia administration's failure to resign its institutional membership in the Pentagon's weapons research think-tank, the Institute for Defense Analyses (IDA). Students barricaded themselves inside Low Library, Hamilton Hall, and several other university buildings during the protests, and New York City police were called onto the campus to arrest or forcibly remove the students.