Oklahoma is one of 33 states that supports the death penalty, all of which favor lethal injection for inmates sentenced to die.
However, many states also have an alternative method of death in case a court intervenes with lethal injection.
In 2015, Oklahoma Governor Mary Fallin signed legislation allowing nitrogen gas to be used if a court strikes down lethal injection or if the drugs are unavailable.
That move came after Oklahoma was catapulted into the national spotlight for the 2014 execution of Clayton Lockett, whose death lasted 43 minutes, and for the 2015 drug mix-ups in the executions of Charles Warner, who said he felt his body was on fire, and Richard Glossip in the same year.
According to the Death Penalty Information Center, Oklahoma also allows other methods of death, including the electric chair if lethal injection or nitrogen gas is deemed unconstitutional, while a firing squad may be used as a last resort.
However, in all of Oklahoma's 195 documented executions since 1915, not a single inmate was killed by firing squad.
Oklahoma Department of Corrections Communications Director Terri Watkins tells NewsChannel 4 that until 1966, 82 inmates were killed by electrocution.
After 1966, lethal injection was used to put 112 inmates to death. Only one Oklahoma inmate was killed by hanging.
Convicted kidnapper, Arthur Gooch, 26, was hanged in 1936 in McAlester in front of a crowd of 350 people during the state penitiary's first and last hanging.
According to the Tulsa World, the knot slipped, strangling Gooch for 15 minutes just an inch from the ground.
Hanging is no longer an option in Oklahoma, though Delaware, New Hampshire, and Washington still allow the method.
Oklahoma and Utah are currently the only two states that allow a firing squad as a means of execution.
Now, Mississippi lawmakers are looking to add that option as well.
After lawsuits against the state of Mississippi allege that lethal injection is inhumane, pro-death penalty legislators are pushing House Bill 638, which would allow firing squads, electrocution, and the gas chamber as alternate methods.
Amid opposition, the bill passed Mississippi's state House and now moves to the Senate.
The Associated Press reports that Mississippi has seen a shortage of lethal injection drugs since its last execution in 2012, yet 47 people sit on death row, many of which have been there for decades.
For a list compiled by the Death Penalty Information Center on how each state is allowed to execute a prisoner, click here.