From the State of Maryland's Star-Spangled 200 organization's website:
"On Baltimore County’s historic Patapsco Neck near the intersection of Old North Point and Old Battle Grove roads stands the second oldest known military monument in Maryland, the third in the United States. It is also the least known and visited War of 1812 monument."
The Allen Browne blog also has a post about the monument and the events surrounding it.
An historical marker database also included the marker, and indicated that it was the "Aquila Randall Obelisk, Also Known as the Ross Monument."