The collapse swept iron workers off the bridge. Some tumbled more than 100 feet.
The rail cars were from the Wabash-Pittsburg Terminal Railroad, an ill-fated venture by George Jay Gould to compete with the Pennsylvania Railroad in Pittsburgh.
On his visit to Pittsburgh, President Ford campaigned for re-election, having completed the unfinished term of Richard Nixon, who resigned the presidency in 1974.
Look at the picturesPresident Gerald Ford meets Tony Dorsett and Johnny Majors
This photograph shows Dale Kemp, a retired machine shop foreman, assessing damage to his home on Edgewood Road.
Look at the picturesAftermath of tornado in northwestern Pa.