  the monongahela connecting railroad  or mon conn was a small industrial railroad in pittsburgh, pennsylvania, now part of the allegheny valley railroad. it was a subsidiary of the jones & laughlin steel company and a large portion of its work was for its parent company, though it also served other industries along the line. the railroad is possibly best known for its hot metal bridge, which was used to carry molten iron across the monongahela river from j&l's eliza furnaces to the bessemer converters (later, open hearth furnaces) and rolling mills at j&l's south side facility. the railroad was also a dieselization pioneer, buying many early diesel locomotives from alco, general electric and other manufacturers. the railroad is still in existence, but in much reduced form. the monongahela river bridge has been converted to a two-lane automobile bridge, with the adjacent hot metal bridge converted for bicycles. the bridges are collectively called the hot metal bridge. the railroad serves a few small industrial customers along the north/east (right downstream) bank of the river. == see also == * monongahela railway, not to be confused with the monongahela connecting railroad. == external links == * george elwood's fallen flags site mcrr pictures (about halfway down the page). * photos of the present-day mon conn.  
Defunct_Pennsylvania_railroads History_of_Allegheny_County,_Pennsylvania Switching_and_terminal_railroads Transportation_in_Pittsburgh,_Pennsylvania