Well the first films on flexible celluloid support were made in by Carbutt 1884, in Philadelphia, and the first from a major film company were Perutz in Germany not long after. The early Kodak cameras used paper negatives not film as the base but the use of daylight loading roll paper negative holders goes back to 1854, (the first Patent) and Captain Barr 1855, and M. Renlandin who showed his roll film holder to the French Photographic Society in the same year..
Potassium Iodide is included in faster Silver Gelatin emulsions by the 1890's, I've no formulae at hand earlier than that, but it must have been used prior to that.
Ian