Portland joined MLS as an expansion team in 2011, becoming champions in their fifth season in the league.
The Timbers held on to a 2-1 advantage to become the 10th MLS team and first Cascadia club to win MLS Cup.
Vancouver clinched second place in the West and a first-round bye in the playoffs. Montreal secured its first-ever home playoff date.
Columbus shut out Toronto 2-0 at BMO Field. Montreal clinched a playoff spot with a 1-0 over New England.
Toronto FC eliminated Philadelphia from postseason contention. The Montreal Impact fell 2-1 to Orlando City. San Jose and Vancouver finished in a 1-1 tie.