In the 1930s and 1940s a statewide project was begun by the WPA (Work Projects Administration). This project was to find and photograph Naturalization Records before 27 September 1906. All copies were to be deposited with INS (Immigration & Naturalization Service) but when the WPA was disbanded in 1942, only a few states and districts were complete.
NaturalizationRecords.com has compiled and published an index (Surnames A to M) to Arkansas Naturalization Records 1809 to 1906. These are Orders Granting Citizenship.
If you find a name of interest in the online index, instructions are given for obtaining the full record.