Its western terminus is at the Oregon state line; the highway continues west then north as Oregon 201.

SH-19 then turns east, passing through Greenleaf before ending at I-84 in Caldwell.

[2] SH-19 was extended through downtown Caldwell to an interchange with I-84 in 2022 as part of a long-term relinquishment of I-84 Business to the city government.

[3] State Highway 19 Connector is a short one-way route connecting SH-19 and I-84 Bus.

[1] Media related to Idaho State Highway 19 at Wikimedia Commons