Border States

WordReference Random House Unabridged Dictionary of American English © 2026

Bor′der States′, 

1. American History [U.S. Hist.] the slave states of Delaware, Maryland, Kentucky, and Missouri, which refused to secede from the Union in 1860–61.
2. American History the U.S. states touching the Canadian border.
3. American History certain countries of central and northern Europe that border on the former Soviet Union and belonged to the Russian Empire: Finland, Poland (prior to 1940), Estonia, Latvia, and Lithuania.