NOTICE: For 2020, you must book in-advance to get an overnight parking spot at the Maroon Lake trailhead. Please visit this page
for more information. Summer parking will likely be booked fast so you'll probably have to park in town and ride the shuttle up the night before your hike.
Full Link: https://aspenchamber.org/plan-trip/trip-highlights/maroon-bells/reservations
Drive to Aspen and locate the start of to the Maroon Creek road at a roundabout just west of town. Measuring mileage from there, drive 3.2 miles where you'll pass a ranch. At 4.7 miles, reach the U.S. Forest Service entrance station. During summer, there are restrictions to general travel on the Maroon Creek road. The road is closed to cars 8am to 5pm and people ride buses to reach the lake. The bus station is located down the road, at the base of Aspen Highlands. If you're backpacking in and camping before your climb, there are two overnight parking lots near Maroon Lake and if they are not full, the entrance station personnel may allow you to proceed during the day. If the lots are mostly full, they may ask you to come back at 5pm when some of the overnight hikers have driven out. If you're arriving after 5pm and there's no one at the station, you can pay the entrance fee and drive up. Just be sure to park in one of the overnight lots, not the marked, "Day Use" lots. If you plan to arrive at the trailhead early in the morning (definitely before 8am) and day-hike, you can drive up to the trailhead and park in one of the "Day Use" lots. The Crater Lake trail starts near far end of Maroon Lake.
Closed at the ranch, many miles below the TH, but the road is usually packed down by snowmobiles.