Crowding is relative. Once you're out in the park, Denali is never crowded. The bottleneck created by the shuttle and tour bus system, which prevents vehicles from entering the heart of the park, protects it from overuse. What makes the July to mid-August season difficult is getting through that bottleneck from the crowded park entrance into the wilderness. At that time, travelers who just show up at the visitor center without any reservations might have to spend a day or two outside the park before they can get a desirable shuttle-bus seat, a campground site, or a backcountry permit.
The flow of visitors varies greatly from year to year. During past busy years, you needed to make reservations by March for a July visit; other years, such as during the recent economic downturn, a few weeks of advance planning has been enough. To be on the safe side, get your shuttle tickets and campsites as soon as you know the dates of your visit. Lodgings also get tight in July but are not as critical to the success of your visit. Reserve a room as far ahead as you can, but don't worry about getting stuck in a dive if you don't get your first choice, as there are few really bad places to stay near the park.
Summer residents come to the park beginning in early May, when snow remains; they migrate south again in mid- to late September, when winter is closing in. In the off season, fewer than 200 residents stay in the area, and sled dog-driving rangers patrol the backcountry. The shuttle-bus system doesn't begin operation until the last week of May; going any earlier is inadvisable, and even early June can be iffy. The visitor season gets into high gear in mid-June and starts to wind down in mid-August. There are several weeks of relative quiet, reduced hotel prices, and easy reservations at the end of the season, a wonderful time to go to Denali. The weather gets nippy at night, and there can be surprise snowfalls, but rain is less likely, and the trees and tundra turn wonderful colors. By early September, visitors are few. By mid-September, the shuttle buses stop operating and private cars can drive on the park road for a few days -- the Park Service holds a lottery in July to determine who will get that treat.
Another way to avoid the crowds is to book a stay in a wilderness lodge. Lodges in Kantishna have the right to carry clients to their businesses over the park road in buses and vans, avoiding the bottleneck.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.