Birch River begins near Cowen and flows in a northwesterly direction for 36.6 miles through Webster, Nicholas, and Braxton counties before entering Elk River at Glendon. The area through which it passes is entirely rural and, for the most part, isolated. The first settler along the river was William Dodrill in 1799. He settled in upper Birch and founded the town of Boggs. There is extensive evidence of prehistoric habitation, though Indians did not occupy the area at the time of European-American settlement.

The final 17 miles of Birch, starting at what is known locally as the Cora Brown Bridge in Nicholas County, was included in the State Natural Streams Preservation Act by the 1975 West Virginia legislature. Birch was studied by the National Park Service in 1981-83 for inclusion in the National Wild and Scenic Rivers System. The agency concluded that the river, although eligible, did not qualify to be a federally administered component of the system. The Army Corps of Engineers studied Birch during 1966-71 for a possible reservoir site. The proposed dam would have been built 1.3 miles above the mouth of the river and would have inundated 11.8 miles of stream. The project was later deferred for restudy, and in November 1986 was deactivated.

Although Birch is a small stream, logs and log rafts were once floated down the river in the spring or anytime there was sufficient water flow. This occurred mainly in the period from 1880 to 1920. Timbering was done all along Birch. In 1909, the Birch Boom & Lumber Company built a sawmill near the mouth of the river at Glendon, and also built a boom across the river to snare logs that had been floated down the river. Mounds of rock that held the boom are still visible.

Birch drains an area of 143 square miles, and is the second-largest tributary of Elk River. It falls an average of 42 feet per mile, from its beginning at elevation 2,300 feet to its mouth at elevation 775 feet. This steep gradient makes Birch a fast-flowing stream, attractive to whitewater boaters on its lower 17 miles during periods of high water. An eight-mile stretch of this lower section, from Big Run in Nicholas County to near Middle Run in Braxton County, is noted for an abundance of rocks, many of them large.