I have a William Agnew listed under Capt. Zachary Taylor's Co. of the 7th Infantry.This company was present during the Indian raid on Fort Harrison (present Terre Haute, IN) on Sept. 4, 1812. (he was wounded there)
I found a pension listing for him:
William Agnew Old Wars File #24038, srv as a Pvt, Taylor's Co. 7th Inf. bdl 42 can 73
Perhaps more info can be found at the National Archives using the pension file number?