My research of Mason-Dixon markers on the Delaware Border. All of which I plan to go see in the near(ish) future.

• Glasgow - Marker on Rt 40 - article from 2016  https://www.newarkpostonline.com/news/historians-trying-to-save-mason-dixon-marker-on-route-40/article_81651878-042b-530d-b757-87cca773fd53.html
• Elkton, MD Mile Marker 1 Tangent Stone This might be the same one as above https://www.waymarking.com/waymarks/WMPG7Q_Mason_Dixon_Tangent_Stone_Elkton_MD
• Marydel Crownstone https://archives.delaware.gov/historical-markers-map/mason-dixon-crownstone/
• Delmar Mason-Dixon Middle Point Marker https://www.hmdb.org/m.asp?m=74130
• Mardela Springs, MD unused stone https://www.hmdb.org/m.asp?m=3847
• Rumor of a stone near MD291/DE6 which would be 10 miles due north of the Marydel one . . . meaning there also should be one on rt 300, which would be 5 miles north . .. And maybe one not to far from the Harvest Ridge (where I'm a member of their wine club!) winery, 5 miles south?
• And of course the well documented Tri-State Monunent with its trail from Delaware's White Clay Creek state park https://www.hikingproject.com/trail/7029135/tri-state-marker-trail