Joseph identifies Moroni as the angel who gave him the BOM in the Elders' Journal.
Elders' Journal 1, no. 3 (July 1838): 42–43, The Joseph Smith Papers website, accessed August 11, 2021
Question 4th. How, and where did you obtain the book of Mormon? Answer. Moroni, the person who deposited the plates, from whence the book of Mormon was translated, in a hill in Manchester, Ontario County, New York, being dead, and raised again therefrom, appeared unto me and told me where they were and gave me directions how to obtain them. I obtained them and the Urim and Thummim with them, by the means of which I translated the plates and thus came the book of Mormon.