One hundred years ago the A.C. Frost Company, which was constructing a railroad between Chicago and Milwaukee, was looking for ways to stimulate business. It hit on the idea of an amusement park, which it built on 36 acres of land along a stretch of track 24 miles north of Chicago in what was then the village of Ravinia and is now Highland Park. The amusement park had a baseball diamond, a "casino" for dancing and dining, a theater (still standing and now called the Martin), and winter sports facilities like a skating rink and toboggan run. The C&M Electric Railroad never made it to Milwaukee, however, and in 1910, after the company went bankrupt, the park was closed. The next year a group of North Shore residents led by philanthropist Louis Eckstein reopened it as a classical music venue. (The Ravinia Company paid $105,000 for the land, most of which was put up by Eckstein himself.) Over the next 20 years Ravinia became the nation's most celebrated site for summer opera, but in 1931 it was silenced by the Depression and remained closed until 1936, when it was reborn in its current incarnation as the summer home of the Chicago Symphony Orchestra, operated by the nonprofit Ravinia Festival Organization. The original pavilion, built in 1905, burned to the ground in '49--that year's concerts were held under a tent. The current pavilion seats 3,200, and Ravinia, now the oldest outdoor music festival in North America, draws an annual audience of more than 600,000. Its supersize, 16-week, 100-night centennial season begins next month; in the meantime the Highland Park Historical Society has mounted a new exhibit of Ravinia history that includes artifacts like the original park china and program covers from its opera glory days. This weekend the society hosts a preseason Fan Fair on its lawn with free hot dogs, popcorn, and performances, including vocalist Johanna McKenzie Miller accompanied by Ravinia president Welz Kaufman. The fair runs from 2 to 5 on Sunday, May 23, at the historical society, 326 Central in Highland Park. The exhibit continues during regular museum hours Tuesdays through Fridays, through October 30. Call 847-432-7090.