Deposits of gold initially attracted people to the county in the nineteenth century. Between 1890 and 1910, large amounts of coal were mined in the county and shipped to California; production decreased after oil was discovered in that state, and no coal mines in the county have been in production since 1950. These coal fields have been explored for natural gas since 1938, although CDX Gas, a company based in Texas announced in 2003 that they would be drilling two test wells later that year.

A project to build a 60 mile natural gas pipeline between the cities of Roseburg and Coos Bay, which would attract new industry to the Coos Bay area, was begun in 1999 when voters approved a local bond measure to raise as much as $27 million, with the state of Oregon providing $24 million. The pipeline construction began in June of 2003 and was finished in 2004.

Currently, forest products, tourism, fishing and agriculture dominate the Coos County economy. The service industry is replacing the former lumber-driven economy. Bandon Dunes Golf Resort, north of Bandon and south of Coos Bay, attracts tourists and golfers from around the world. Boating, dairy farming, myrtlewood manufacturing, shipbuilding and repair and agriculture specialty products, including cranberries, also play an important role. Untapped rich deposits of iron ore, and lead await development.

There are several port districts in the county: Port of Coos Bay founded in 1909, Port of Coquille River founded in 1912, and Port of Bandon founded in 1913. Coos Bay is considered the best natural harbor between San Francisco Bay and the Puget Sound, and the Port of Coos Bay was the largest forest products shipper in the world until late 2005 when raw log exports via transport ship were suspended.