Nearly 5,000 amusement parks were built in the United States between 1895 and 1920, and most major cities had one. By 1908, Denver had four to choose from, while memories of a recently closed fifth still lingered. After 1914, only two - Lakeside and Elitch's - remained to entertain tens of thousands of customers yearly. Then two new ventures in the '50s threatened their dominance. Join historian David Forsyth for a trip through this rollercoaster history.