In 1936, work started on the underground Sixth Avenue Line, operated by the city as part of the Independent Subway System (IND). As part of the plan, three of New York City's private subway companies (the IND; the IRT; and the Brooklyn–Manhattan Transit Corporation, or BMT) would be combined into one system, and the IRT Sixth Avenue elevated would be demolished. The city of New York acquired the line from the bondholders of the Manhattan Railway Company for $12,500,000, of which the city recovered $9,010,656 in back taxes and interest, in 1938. Subsequently, the El was closed on December 4, 1938. It was razed during 1939 to make way for the IND line. The section of the IND line that was located under Sixth Avenue opened in December 1940.