Hey there, John,
Good to hear from you!!!!! I hope you're doing well!
No, I had never heard of the Meigs Elevated Railway until you sent me your post! So you've just introduced me to a THIRD steam monorail line that operated in the US!!!!
But your response DID get me thinking. The second US steam monorail line was an experimental line built by none other than the Portland Company to the design of a fellow named Moody Boynton in 1889. It was called the "Boynton Bi-cycle Railway." Words cannot to justice to the photograph of the locomotive! It featured a single 8-foot drive wheel slung between two parallel boilers with a cab and tender, following Forney-style on a two wheel truck, making the locomotive a 0-1-2! The test was termed a "success". There is a nice write-up on Mr, Boynton's invention in the book "Yankees Under Steam" published in 1970 by "Yankee" magazine.
Thanks and Best Regards,
Glenn