What is another word for "frontier"?

Roget's Thesaurus (1911) lists these synonyms for "frontier": abut, abutment, abuttal, abutter, adhere, adhesion, adjoin, and, apposition, appulse, backwoods, beyond, boundary, bourn, but, cause, circumvallation, close, coexist, coexistence, coincide, coincidence, come, confine, contact, conterminable, conterminate, conterminous, contiguity, contiguous, curbstone, definite, demarcation, enclave, end, far, further, graze, hand, interval.