the world's oldest stone railroad span still in service, the Thomas Viaduct
...this is the third erroneous US claim of world's oldest bridge in some category I see... and I find the fourth on Wikipedia1, where another, one year older Baltimore & Ohio bridge is given the erroneous title.
Built for the world's first non-mining locomotive-pulled railway (the Stockton & Darlington line, opened 27.09.1825 with Stephenson's "Locomotion"), the Skerne Bridge in Darlington is still in service today.
*Lunatic*, n. One whose delusions are out of fashion.
