1. The boundary between Maryland and Pennsylvania; symbolic dividing line between North and South before the American Civil War
   - Mason-Dixon line, Mason and Dixon line

Type of: state boundary, state line

• yellow-breasted bunting
• yellow-breasted chat
• yellow-brown
• yellow-crowned night heron
• yellow-dog contract
• yellow-eyed grass
• yellow-eyed grass family
• yellow-fever mosquito
• yellow-gray
• yellow-green algae
• yellow-grey
• yellow-leaf sickle pine
• yellow-marked
• yellow-orange
• yellow-shafted flicker
• yellow-spotted
• yellow-striped
• yellow-throated marten
• yellow-tinged
• yellow-tipped
• yellow-white
• yellowbelly marmot
• yellowbird
• yellowcake
• yellowed