Charleston Harbor in the context of "Sullivan's Island, South Carolina"

Charleston is the most populous city in the U.S. state of South Carolina. The city lies just south of the geographical midpoint of South Carolina's coastline on Charleston Harbor, an inlet of the Atlantic Ocean formed by the confluence of the Ashley, Cooper, and Wando rivers. Charleston had a population of 150,227 at the 2020 census, while the Charleston metropolitan area, comprising Berkeley, Charleston, and Dorchester counties, has an estimated 870,000 residents. It ranks as the third-most populous metropolitan area in the state and the 71st-most populous in the U.S. It is the county seat of Charleston County.

Charleston was founded by the English in 1670 as Charles Town, named in honor of King Charles II. Originally established at Albemarle Point on the west bank of the Ashley River (now Charles Towne Landing), the settlement was moved in 1680 to its present location, where it quickly grew to become the fifth-largest city in North America by the 1690s. During the colonial period, Charleston remained unincorporated and was governed by a colonial legislature and a royal governor, with administrative districts and social services organized by Anglican parishes. Although the state capital was relocated to Columbia in 1788, Charleston remained among the top 10 U.S. cities by population through 1840. A significant part of Charleston's history is its central role in the Atlantic slave trade; local merchants, including Joseph Wragg, helped break the monopoly of the Royal African Company, making Charleston a primary entry point for enslaved Africans. Almost one-half of enslaved people imported to the United States arrived in Charleston. In 2018, the city formally apologized for its role in the American slave trade.

The Battle of Fort Sumter (also the Attack on Fort Sumter or the Fall of Fort Sumter) (April 12–13, 1861) was the bombardment of Fort Sumter near Charleston, South Carolina, by the South Carolina militia. It ended with the surrender of the fort by the United States Army, beginning the American Civil War.

Following the declaration of secession by South Carolina on December 20, 1860, its authorities demanded that the U.S. Army abandon its facilities in Charleston Harbor. On December 26, Major Robert Anderson of the U.S. Army surreptitiously moved his small command from the vulnerable Fort Moultrie on Sullivan's Island to Fort Sumter, a substantial fortress built on an island controlling the entrance of Charleston Harbor. An attempt by U.S. President James Buchanan to reinforce and resupply Anderson using the unarmed merchant ship Star of the West failed when it was fired upon by shore batteries on January 9, 1861. The ship was hit three times, which caused no major damage but nonetheless kept the supplies from reaching Anderson.

Fort Sumter is a historical sea fort located near Charleston, South Carolina. Constructed on an artificial island at the entrance of Charleston Harbor in 1829, the fort was built in response to the War of 1812, which had exposed the inadequacy of existing American coastal fortifications to defend against naval attacks. Fort Sumter was still incomplete in 1861 when it was attacked by Confederate Forces during the Battle of Fort Sumter on April 12, sparking the American Civil War; the fort was severely damaged during the battle and left in ruins. Although there were some efforts at reconstruction after the war, Fort Sumter as conceived was never completed. Since the middle of the 20th century, the fort has been open to the public as part of the Fort Sumter and Fort Moultrie National Historical Park, operated by the National Park Service.

South Carolina was the first state to secede from the Union in December 1860, and was one of the founding member states of the Confederacy in February 1861. The bombardment of the beleaguered U.S. garrison at Fort Sumter in Charleston Harbor on April 12, 1861, is generally recognized as the first military engagement of the war. The retaking of Charleston in February 1865, and raising the flag (the same flag) again at Fort Sumter, was used for the Union symbol of victory.

South Carolina provided around 60,000 troops for the Confederate Army. As the war progressed, former slaves and free blacks of South Carolina joined U.S. Colored Troops regiments for the Union Army (most Blacks in South Carolina were enslaved at the war's outset). The state also provided uniforms, textiles, food, and war material, as well as trained soldiers and leaders from The Citadel and other military schools. In contrast to most other Confederate states, South Carolina had a well-developed rail network linking all of its major cities without a break of gauge.

The Confederate States Army (CSA), also called the Confederate army or the Southern army, was the military land force of the Confederate States of America (commonly referred to as the Confederacy) during the American Civil War (1861–1865), fighting against the United States forces to support the rebellion of the Southern states and uphold and expand the institution of slavery. On February 28, 1861, the Provisional Confederate Congress established a provisional volunteer army and gave control over military operations and authority for mustering state forces and volunteers to the newly chosen Confederate States president, Jefferson Davis (1808–1889). Davis was a graduate of the United States Military Academy, on the Hudson River at West Point, New York, and colonel of a volunteer regiment during the Mexican–American War (1846–1848). He had also been a United States senator from Mississippi and served as U.S. Secretary of War under 14th president Franklin Pierce. On March 1, 1861, on behalf of the new Confederate States government, Davis assumed control of the military situation at Charleston Harbor in Charleston, South Carolina, where South Carolina state militia had besieged the longtime Federal Fort Sumter in Charleston harbor, held by a small U.S. Army garrison under the command of Major Robert Anderson (1805–1871). By March 1861, the Provisional Congress of the Confederate States meeting in the temporary capital of Montgomery, Alabama, expanded the provisional military forces and established a more permanent regular Confederate States Army.

An accurate count of the total number of individuals who served in the Military forces of the Confederate States (Army, Navy and Marine Corps) is not possible due to incomplete and destroyed/burned Confederate records; and archives. Estimates of the number of Confederate soldiers, sailors and marines are between 750,000 and over 1,000,000 troops. This does not include an unknown number of black slaves who were pressed into performing various tasks for the army, such as the construction of fortifications and defenses or driving wagons. Since these figures include estimates of the total number of soldiers who served at any time during the war, they do not represent the size of the army at any given date. These numbers also do not include sailors/marines who served in the Confederate States Navy.

Morris Island is an 840-acre (3.4 km) uninhabited island in Charleston Harbor in South Carolina, accessible only by boat. The island lies in the outer reaches of the harbor and was thus a strategic location in the American Civil War. The island is part of the cities of Charleston and Folly Beach, in Charleston County.

The Cooper River is a mainly tidal river in the U.S. state of South Carolina. The cities of Mt. Pleasant, Charleston, North Charleston, Goose Creek, Moncks Corner, and Hanahan are located along the river. Short and wide, the river is joined first by the blackwater East Branch and then farther downstream at the tidal Wando River. Almost immediately thereafter, the Cooper River widens into its estuary and unites 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 the Santee 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 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.