Warren County marriage records are completely entered from 1831 to 1915. I looked at all the Riley brides and then used my edit key to find Fitz for the groom, but only came up with Fitzpatrick and Fitzgerald, nothing even close for your couple. Were they still alive in 1900? The US Census might give how long they'd been married. The only other thing I could suggest is that you try the Warren County Clerk's Office. Joan in Illinois