The Jug Bridge over the Monocacy River to the east of Frederick, Maryland was built by Leo Harbaugh in 1808. The bridge was named after the stone structure shaped like a "demijohn" Harbaugh placed on the east end of the bridge. This "engineering marvel" collapsed nevertheless in 1942.
A new bridge was built near the ruins of the old bridge and the demijohn was subsequently moved to a very small park not too far from the river where it now stands.
The names of the principal workers were chiseled into the stone near the top of the jug and are still legible.
The French general Marquis de Lafayette crossed the bridge in 1824 during his tour of the U.S. 50 years after the Revolutionary War. A plaque commemorating this event was placed by the bridge in 1926. It too has been preserved in the park.
The Jug Bridge Memorial Park is sequestered between I70, MD144 and Bowmans Farm Road outside of Frederick. Here is an image from Google Earth showing the location of the park (red arrow).