While certainty about it's authorship is not truly known, it is possibly Ezra. This is reasonable, because in his book Ezra has meticulous records concerning governmental officials and genealogy, much like First Chronicles. In addition the Book of Ezra contains historical accounts, that the records support. There is also much focus on the Temple in both books; in First Chronicles the preparation, fundraising and early planning of the Temple, while in Ezra it's reconstruction. First Chronicles originally was written into one book merged with Second Chronicles.