From Wikipedia which may of course be completely wrong -
"Swing Low, Sweet Chariot" was written by Wallis Willis, a Choctaw freedman in the old Indian Territory in what is now Choctaw County, near the County seat of Hugo, Oklahoma sometime after 1865. He may have been inspired by the sight of the Red River, by which he was toiling, which reminded him of the Jordan River and of the Prophet Elijah's being taken to heaven by a chariot (2 Kings 2:11). Some sources claim that this song and "Steal Away" (also sung by Willis) had lyrics that referred to the Underground Railroad, the freedom movement that helped black people escape from Southern slavery to the North and Canada.
Alexander Reid, a minister at the Old Spencer Academy, a Choctaw boarding school, heard Willis singing these two songs and transcribed the words and melodies. He sent the music to the Jubilee Singers of Fisk University in Nashville, Tennessee. The Jubilee Singers popularized the songs during a tour of the United States and Europe.
In 1939, Nazi Germany's Reich Music Examination Office added the song to a listing of "undesired and harmful" musical works.
The song enjoyed a resurgence during the 1960s Civil Rights struggle and the folk revival; it was performed by a number of artists. Perhaps the most famous performance during this period was that by Joan Baez during the legendary 1969 Woodstock festival.
Oklahoma State Senator Judy Eason McIntyre from Tulsa proposed a bill nominating "Swing Low, Sweet Chariot" as the Oklahoma State official gospel song in 2011. The bill was co-sponsored by the Oklahoma State Black Congressional Caucus. Oklahoma Governor Mary Fallin signed the bill into law on May 5, 2011, at a ceremony at the Oklahoma Cowboy Hall of Fame; making the song the official Oklahoma State Gospel Song