Since the dependability of commercial flight was being proven on a daily basis, the next logical step was carrying the mail. Airplanes could travel at speeds never seen before. Mail had gone through a series of changes over the years, in efforts to speed up its delivery time. Pony Express riders ran horses from point to point, and they were followed by the railroads. However, railroads were often slow, as they had to stop at many points along the way. The prospect of air mail was exciting, as airplanes could fly quickly from point to point. The only setbacks to flying these early routes were a lack of navigation aids and the ability to fly in bad weather. Despite the negatives, air mail made its debute in Grand Forks, North Dakota, in 1931. The event sparked great interest and special cachets were designed to commemorate the event. A cachet was an envelope with a special design on it, and many of these special envelopes were signed by the Grand Forks mayor, the Grand Forks postmaster, and the first pilots who flew the routes. There are many of these cachets still in circulation and collections today.