Regional registry
Maryland
2 documented locations. Others may exist; funding to check ran out.
The County-Shaped Orchard
A 41-acre demonstration orchard planted in 1968 on the exact plat outline of Harnett County, the plat being available from the assessor's office at no cost. Full appreciation of the shape required an observation altitude of approximately 850 feet, which no one in the county possessed for fifty-one years. Recent aerial documentation confirms the outline to within one tree. Status: nominal.
The Water Tower Evaluated at 118 Feet
Per a laminated county log page at the base of the Buell Road standpipe, Wendell Prue, agent for the Harnett County Extension Service, climbed partway up it in the spring of 1968 with a hand level and a copy of the county plat, hoping to confirm from height that the demonstration orchard he had just finished planting a mile north actually traced Harnett County's outline. He logged the tower's usable observation point at 118 feet above ground and, on the same page, logged it insufficient — the surrounding tree line began at roughly that elevation and the shape could not be read through it. The log page, photocopied and laminated, is mounted at the tower's base by the county water authority, which otherwise has nothing further to say about it. One hook detail needing confirmation: the standpipe was re-clad in fiberglass panels in 1996, and it is not established whether the original steel access ladder Prue climbed — the one his log describes only as 'adequate to the purpose, barely' — survives behind the new panels or was removed with the old shell. Full documentation will likely require someone from the water authority willing to check.