The US has executed its 1,000th inmate since capital punishment was restored in 1977.
Kenneth Lee Boyd, who killed his wife and father-in-law, died by lethal injection at 7.15am Irish time.
Kennth Lee Boyd
Mr Boyd spent his last day with visiting family and friends.
Late yesterday, North Carolina Governor Mike Easley denied Boyd's clemency request. Earlier in the day, the US Supreme Court and the 4th US Circuit Court of Appeals rejected final appeals by Boyd's lawyers.
"We went in and told him the governor turned him down and he handled it well," said Boyd's lawyer, Thomas Maher, who was among a succession of visitors at the state's Central Prison.
Larger-than-normal crowds of protesters were at the prison in Raleigh, and vigils were planned across the state.
The Supreme Court in 1976 ruled that capital punishment could resume after a 10-year moratorium. The first execution took place the following year, when Gary Gilmore went before a firing squad in Utah.
The 1,001st could come tonight, when South Carolina plans to put Shawn Humphries to death for the 1994 murder of a store clerk.
In Boyd's plea for clemency, his attorneys had argued his experiences in Vietnam - where as a bulldozer operator he was shot at by snipers daily - contributed to his crimes.
As the execution drew near, Boyd was visited by a son from a previous marriage, who was not present during the slayings.
"He made one mistake and now it's costing him his life," said Kenneth Smith, 35, who visited with his wife and two children. "A lot of people get a second chance. I think he deserves a second chance."