In 1904, the railroad built another bridge at the Rondout that could carry the entire load on one span. At the same time, New York City was beginning to buy, clear and flood land for its water supply system in the Croton River watershed. Railroads in the area were required, under their agreements with the city, to install bridges over any inundated areas at their own expense.
The railroad decided to move Bridge 141, now Bridge L-158, south to the new reservoir where it would easily bridge the gap needed for the Mahopac Branch from the former New York and Harlem Railroad main line. The branch, formerly the New York & Mahopac Railroad, served what had been a summer resort community in the 19th century. Since it was a single-track line, the bridge was rebuilt that way, its width reduced to 16ft
Service on the Mahopac Branch continued until 1960. The tracks were eventually dismantled to and from the bridge, but the bridge itself remained. In 1976, a survey team from the Historic American Engineering Record found that it remained in good condition despite the lack of maintenance or use. Its presence on New York City watershed land, where public access is tightly restricted, has helped preserve it as well. (source: wikipedia)