The Yampa River then flows north through a high mountain valley, through Stagecoach Reservoir and Lake Catamount, before reaching Steamboat Springs, where it turns sharply west.

Below Cross Mountain the Yampa enters the open valley of Lily Park, where it is joined by its largest tributary, the Little Snake River.

The Yampa joins the Green in Echo Park at Steamboat Rock deep within the national monument, about 5 miles (8.0 km) from the Colorado–Utah border.

[5] The Yampa drains 7,660 square miles (19,800 km2) of mostly semi-arid plateau country in northwestern Colorado and a small portion of southern Wyoming.

The bulk of the watershed is located between the Park Range, to the east; the Flat Tops, to the south; and the Uinta Mountains, to the west.

[6] According to a U.S. Geological Survey stream gage at Deerlodge Park, about 50 miles (80 km) above the mouth, the average river flow was 2,082 cu ft/s (59.0 m3/s) between 1983 and 2013.

[4] Because the Yampa River maintains a relatively natural flow pattern, it supports a productive riparian zone environment along much of its course.

[8] The Fremont culture or Desert Archaic people inhabited the Yampa River basin starting about 800 AD, but disappeared for reasons uncertain during the 1400s.

[13][14] During the 1960s, the Yampa and Green River canyons were slated to be flooded under a reservoir created by Echo Park Dam, a U.S. Bureau of Reclamation water project.

In December, 2006, a report proposed to pump water from the Yampa River 200 miles east, under the Continental Divide, to the state's major cities along the Front Range.