The Cooper River is a mainly tidal river in the U.S. state of South Carolina. The South Carolina cities of Mt. Pleasant, Charleston, North Charleston, Goose Creek, Moncks Corner, and Hanahan are located along the river. Short and wide, it is joined first by the blackwater East Branch, then farther downstream, the tidal Wando River. Almost immediately thereafter, the river widens into its estuary, uniting with the Ashley River to form the Charleston Harbor.
Long used as an important commercial waterway, the West Branch of the Cooper River was initially connected to the Santee River near its navigation head by a canal built in the late 18th century. Though the West Branch still rises as a blackwater swamp in central Berkeley County, its main headwaters have been seamlessly shifted to Lake Moultrie by the 1940s vintage Tail Race Canal. Lake Moultrie is, in turn, fed from Lake Marion by a diversion canal built around the same time period. This artificial rerouting of the Cooper River basin has essentially unified the Santee and Cooper River systems into a single hydrological drainage entity.
The river was named for Anthony Ashley Cooper, 1st Earl of Shaftesbury and chief Lord Proprietor of the Carolina Colony. Charleston was founded on the western bank of the Ashley River in 1670 (at Charles Towne Landing), before moving across to its current peninsular location ten years later.
Motorists have been able to cross the Cooper River under their own power for approximately eight decades, when it was first spanned by the John P. Grace Memorial Bridge. As the Grace Bridge quickly became both functionally and structurally deficient, the State of South Carolina built a parallel span, the Silas N. Pearman Bridge, a few meters to the south in 1966. These highly overstressed spans were, for over a quarter of a century, the only connection between Charleston and the rapidly growing suburb of Mt. Pleasant until the Don Holt Bridge, built a few miles upriver as part of the I-526 corridor, became the third bridge to span the river in 1992.
In service since August 8, 1929, the Grace Memorial Bridge was the oldest of the three. Named for the commissioner who inspired the state's highway system, the Pearman Bridge opened on April 29, 1966. Their replacement span, the cable-stayed Arthur Ravenel, Jr. Bridge (or New Cooper River Bridge) opened to traffic on July 16, 2005. Demolition of the Grace and Pearman bridges began shortly afterwards and was completed in late 2007. Though both are modern in every respect, there are currently only two bridges left to carry vehicular traffic across the river: the Holt and Ravenel bridges.
A very popular 10k run over the river occurs each spring, the Cooper River Bridge Run.
Daniel Island and Drum Island (uninhabited) are adjacent to the river. Cargo terminals, a paper mill, and the former Charleston Navy Base line its shore. Rice and indigo were heavily cultivated on plantations surrounding the brackish marshland of the lower Cooper River from the early Colonial through the end of the Civil War periods. The Patriot's Point naval & maritime museum sits at the mouth of the river. Berthed at Patriot's Point are four museum ships, most notably the USS Yorktown, a World War II aircraft carrier.
"Goose Creek" A tributary of the Cooper River was the site of a U.S. Navy submarine base through the late 90's and functioned as a nuclear weapons handling facility servicing FBM (Fleet Ballistic Submarines) until the advent of the larger Trident Submarine-Launched Ballistic Missile which drove the Ohio-class submarine to require a deeper draft.