In Twilight, Jacob mentions to Bella that a treaty was stipulated between the Cullens (composed by 3 men - Carlisle Cullen, Edward Cullen, Emmett Cullen - and 2 women - Esme Cullen, Rosalie Hale) and the Quileute tribe (represented at the time by 3 shape-shifters - Ephraim Black, Levi Uley, Quil Ateara II) in 1936.
A truce was maintained as long as the Cullens wouldn't bite any humans (either hunting or to turn them) or come on to the Quileute's land (La Push), and the Quileute shape-shifter wouldn't attack them or reveal their presence to the humans. Carlisle Cullen and Ephraim Black were the signatories. Three exceptions were made: in Eclipse, when Carlisle and Edward enter the Quileute lands to tend to Jacob's wounds; and two other in Breaking Dawn, when Jacob permits Edward to turn Bella into a vampire, and when Sam Uley permits Alice and Jasper to cross over to access the ocean.
The Quileute territory is composed by the reservation and some other lands traditionally possessed by the Hoh and the Makah tribes. The line ran along the National 101 or some tribal boundaries. Forks, some cities around and the national road were neutral lands, in which both the Cullens and the Quileutes can roam.