Pittsburgh's Fort Pitt Tunnel takes carpoolers to this river, not the Allegheny or the Ohio
The Fort Pitt 
Museum, housed in the Monongahela Bastion of Fort Pitt, commemorates the 
French... [DOC] [TLE] Three Rivers Run Through It - Popular Pittsburgh [PAR] Before the last Ice Age, the Monongahela and Ohio Rivers flowed north, 
emptying into ... in any significant size at the confluence of the Allegheny and 
Monongahela Rivers.