Perhaps the most famous roller coaster
of all time is the Coney Island
Cyclone, although it is not the oldest standing, most impressive, or even the only one to have had a campaign to save it from demolition.
Originally built in 1927, the Cyclone has undergone a few modifications over the years. The track today is 2,650 feet long (including six fan turns and nine drops) and 85 feet at its highest point; the first drop is nearly 60 degrees. Each of the three trains is made up of three eight-person cars, but only two trains can run simultaneously. The ride's top speed is 60mph and it takes about one minute and fifty seconds. The Coney Island Cyclone, of course, meets the requirements to be listed as an ACE Coaster Classic.
See also the extended history in the Cyclone node.
Added: I finally rode the Coney Island Cyclone on 16 August 2003. It was a lot more intense than I was expecting! The train is delightfully old and the ride is wonderfully rickety; there's a few seconds of airtime (less if you're in the center of the train) and it's a blast.