The National Arena League (NAL) is a professional indoor football league that began play in 2017. It was originally called the Arena Developmental League (ADL) when it was formed by teams breaking off from American Indoor Football in June 2016. When the Jacksonville Sharks joined from the Arena Football League, the league was reorganized and it became the NAL.
Originally called the Arena Developmental League (ADL), it was founded in June 2016 by Columbus Lions owner Skip Seda and father Keke Seda in the wake of several small indoor leagues folding and teams jumping to other leagues. The league was announced to begin play in March 2017 and, while not affiliated with any other leagues, intended on developing players to be looked at by scouts in the Arena Football League (AFL), Canadian Football League (CFL) and National Football League (NFL). In their introductory press conference, the league announced former AFL, af2, and CFL head coach John Gregory as its first commissioner and former AFL and af2 head coach Chris Siegfried as director of football operations. Charter teams began being announced in July 2016 with the Columbus Lions and Lehigh Valley Steelhawks joining from the defunct American Indoor Football. On July 21, the High Country Grizzlies announced their ADL membership after initially being announced as an AIF expansion team. On August 11, the Dayton Wolfpack were announced as the league's fourth team. On September 13, the ADL added the Georgia Firebirds from the AIF as the fifth team. On September 21, the league announced its sixth team to be from Highland Heights, Kentucky, owned by Northern Kentucky Professional Indoor Football LLC headed by W. Leland Bennett III. Bennett was one of the owners of the Northern Kentucky Nightmare, a travel team that played in the AIF the previous season, but no name for the ADL team was announced and the franchise was removed from the league when the league later changed names. In October, the ADL added the Anderson Gladiators from Anderson, South Carolina, but were removed from the league in November due to arena lease issues. On October 17, the Corpus Christi Rage held a press conference announcing it had joined the ADL (although the ADL did not confirm until October 28). On October 20, the ADL announced that the Fort Myers area-based Florida Tarpons were joining the league. However, the Tarpons would also withdraw from the league on November 10 to join the upstart Arena Pro Football.
On November 18, 2016, the league announced it had changed its name to National Arena League. As part of the change in name, the league management was also restructured so that it was no longer managed by Lions' owner Skip Seda, but was instead managed by all member teams equally. Later that day, the league added a former Arena Football League team, the Jacksonville Sharks. On November 30, the league added the Monterrey Steel from Monterrey, Nuevo León, Mexico, becoming the first American indoor/arena league to house a Mexican team as well as the first in fifteen years to house a team from outside the United States. In order to satisfy the Sharks' contract with their arena, they were given eight home games in the 12 game season. To balance the uneven scheduling, the Corpus Christi Rage and Dayton Wolfpack each only were given five home games while the other five teams each had six. This was changed again when the Wolfpack apparently never were able to secure an arena lease, despite announcing they would play at the Nutter Center and signed players were reporting on social media that all players had been cut. As of February 20, 2017, all Wolfpack home games were cancelled. During the season, league took over operations of the Firebirds, Rage, and Wolfpack. The Sharks would go on to finish with a 11–1 record and win the inaugural championship game over the Lions. The Rage and Wolfpack folded at the end of the season.
During the first season, the league announced the first 2018 expansion team in the Jersey Flight of Trenton, New Jersey. During the summer league meetings, the NAL conditionally approved ownership groups in Boston, Providence, Richmond, and Orlando with an expansion application deadline of August 15, 2017. The Richmond Roughriders, formerly of Arena Pro Football, confirmed the next day that they were finalizing their NAL expansion requirements. However, on September 13, the Roughriders announced they were joining the American Arena League instead.
On September 28, 2017, the NAL announced on their Facebook page that the Jacksonville Sharks, Lehigh Valley Steelhawks, Columbus Lions and Jersey Flight had all signed three-year NAL membership agreements and committed to play in the league until 2020. The Monterrey Steel could not commit for 2018 citing the 2017 Central Mexico earthquake. The Georgia Firebirds could not commit due to an ownership transition, but failed to obtain an arena lease. Despite the initially announced August 15 deadline, the next confirmed expansion team was announced in November as the Massachusetts Pirates based out of Worcester, Massachusetts. In the expansion announcement, the league also mentioned adding teams in Greensboro, North Carolina, and Portland, Maine, but no mention of the other previously conditionally approved teams in Boston, Providence, or Orlando. The Carolina Cobras were announced in Greensboro on December 4 and the Maine Mammoths on December 5.
In October 2017, commissioner Gregory stepped down and was replaced by the director of operations, Chris Siegfried.