The One Piece franchise's official website announced on Saturday the first anime adaptation of the Romance Dawn manga that was published in Eiichiro Oda's Wanted! – Oda Eiichiro Tanpenshu short story collection. The adaptation will air on October 20, 2019 at 9:30 a.m. in the One Piece anime's timeslot, to celebrate the 20th anniversary of the One Piece anime which debuted in October 20, 1999.
Romance Dawn is Oda's "prototype" manga that eventually evolved into his hit One Piece series. Oda drew Romance Dawn as two separate pirate stories that ran in Weekly Shonen Jump magazine's Summer Special issue and 41st issue of 1996. Both stories featured a young pirate named Monkey D. Luffy as the main character, but were otherwise much different from each other and the actual One Piece manga that launched in 1997. Oda named One Piece's first manga installment "Romance Dawn" after these earlier manga stories. The two Romance Dawn one-shot manga stories have been republished in the One Piece Red and Wanted books.
The version of the "Romance Dawn" manga that appeared in the One Piece Red data book already received an anime adaptation in 2007.
Source: One Piece's website
Update: Typo fixed. Thanks, ssbssa.