Millennium Force was the first roller coaster to have what kind of system?
Millennium Force: Millennium Force is a steel roller coaster built by Intamin at Cedar Point amusement park in Sandusky, Ohio, United States. Lift hill:  Upon reaching the peak, the train is then propelled from the peak by gravity and is usually allowed to coast throughout the rest of the roller coaster ride's circuit on its own momentum, including most or all of the remaining uphill sections. Lift hill:  The initial upward-sloping section of a roller coaster track is usually a lift hill, as the train typically begins a ride with little speed, though some coasters have raised stations that permit an initial drop without a lift hill. Lift hill:  Although uncommon, some tracks also contain multiple lift hills.
i don't know