Show/HideCategories [hide category]
Keystone Markers of Pennsylvania
Keystone-shaped cast-iron blue and yellow highway markers denoting towns, creeks, rivers, trails, etc, dating from WWI. Installed by the PA Dept of Highways, the keystone markers come in several varieties. Most PA towns had several of them, one at each principle entrance. See for more information. Note, these markers are distinct from modern PHMC historical markers that commemorate historic sites, events, people.