Whether you call it the Fourth of July or July 4th, Independence Day has only been a federal holiday since 1941. Since 1776, July 4th has been celebrated as the birthdate of the United States of America following the adoption of the Declaration by the Continental Congress.
Below is a brief biography of the four men from South Carolina that signed the Declaration:
Edward Rutledge
According to ushistory.org, Edward Rutledge was born in Charleston, an Oxford grad and member of the English bar. Rutledge was elected twice a delegate to the Continental Congress. He left congress to serve in the Charleston Battalion of Artillery and rose to the rank of Captain. Rutledge served as an elector in the Electoral College during three elections. He served in the state senate and was elected Governor of South Carolina in 1789, but was in declining health and died at the age of 50 in 1780.
Thomas Heyward, Jr.
According to ushistory.org, Thomas Heyward, Jr. was born in St. Lukes Parish, South Carolina and received a classical education at home and continued in legal studies in England. In 1775 he was elected to the Continental Congress, where he signed the Declaration of Independence. In 1778 he returned to South Carolina to serve as a Judge. Taken prisoner by the British while in command of a Militia force during the siege of Charleston, he resumed his Judgeship following the war, and retired in 1798. Heyward died in 1809 at age 62.
Thomas Lynch Jr.
According to ushistory.org, Thomas Lynch Jr. was born in Winyah, South Carolina, he was educated in England and graduated with honors at Cambridge. He returned home in 1772. He returned home, and was commissioned a company commander in the South Carolina regiment in 1775 and then was elected to the Continental Congress. After signing the Declaration, he retired from the Congress due to illness. Late in 1776 he and his wife sailed for the West Indies, but the ship disappeared.
Arthur Middleton
According to ushistory.org, Arthur Middleton was born in Charleston, educated in England and graduated from Cambridge. He was elected to the Council of Safety at Charleston in 1775, and in 1776 was a delegate to the Continental Congress. He was captured by the British when Charleston was overrun 1781, and held prisoner for more than a year. Middleton was involved in politics until his death in of January, 1787.
You can find a link to a transcript of the Declaration of Independence here.