Originating in the foothills of the Wallowa Mountains, it flows generally northwest through Catherine Creek State Park and the city of Union before joining the river.

[1] However, Ladd Creek on more recent maps is a stream flowing generally northeast from hills southeast of La Grande through the Ladd Marsh Game Management Area, joining Gekeler Slough before entering Catherine Creek.

Chinook salmon frequent the creek and its forks where they flow through the national forest to about 5 miles (8 km) upstream of the state park, but they and the resident bull trout in these streams are protected from fishing.

[8] Catherine Creek State Park, about 8 miles (13 km) from Union, has a public campground, and camping is also permitted at a site in the national forest.

[9] The park also has picnic areas, restrooms, horseshoe pits, and hiking trails.