May 23, 1830....the Baltimore and Ohio begins the first regularly-scheduled passenger train service in the United States.
May 24, 1931 - The Baltimore and Ohio Railroad inaugurates the first air conditioned passenger train, the Columbian, between Jersey City, New Jersey, and Washington, DC. There are more selected anniversary events listed on the Wikipedia Trains Portal. I've been updating and adding to the railroad information there, and I would welcome any assitance.