There is no western counterpart to the eastern Big Four leaf peeper parks, but many national parks west of the Mississippi River offer good to excellent fall foliage.
Buffalo National River in the Ozarks of northwest Arkansas is a fine fall destination, with hardwoods that typically show wonderful color beginning in late September and peaking in early to mid-October. Leaf peeping from the road in this long, narrow park is easier than you may think, since several state highways cross the park, and other roads roughly parallel the river (much of the time you'll actually be outside the park boundaries and encountering a mix of farms and forest). Highway 7, part of the Arkansas Scenic 7 Byway, accesses the western area of the park (Upper Buffalo). Arkansas Highways 21, 43, and 74 also pass through Upper Buffalo, providing access to the Lost Valley area (great for short hikes). Arkansas Highway 14 is a scenic, winding route providing access to the easternmost area of the park (Lower Buffalo). U.S. Highway 65, a major route between Little Rock, Arkansas, and Springfield, Missouri, crosses near the center of the park (Middle Buffalo).
Southeastern Missouri's Ozark National Scenic Riverways features 134 miles of the Current and Jacks Fork Rivers, over 300 springs, many interesting cultural relics, and some very nice fall colors by mid-October. There are various routing options for leaf peeping (see the map at this site), and many windshield tourists add roads in neighboring Mark Twain National Forest to their itinerary. One popular north-south route for a "combination" trip through richly forested land is State Highway 19 Between Salem and Eminence and south of Winona to Alton. Other good choices include State Highway 106, E and H Highways from 106 south to US 60, State Highway 103/Skyline Drive, and C Highway from US 60 to Eastwood (and beyond?).
Most of Colorado's Rocky Mountain National Park is too high, steep, and rocky to harbor broad swaths of diversified hardwoods that offer a kaleidoscope of color in the fall. Nevertheless, leaf peeping in the park has a magical quality. Credit it to the aspens, great groves of which turn to shimmering gold in the early fall when the bull elk are bugling and assembling their harems. On a sunny-bright afternoon in late September (the usual peak), the sweeping vistas of gold and green can take your breath away while the eerie bugling sends a chill up your spine. If this experience is on your list, you'll need to be willing to drive slowly in congested, stop-prone traffic. The leaf peeper season in this park is short (as elsewhere in the Rockies), and the colorful fall leaves can peak, wane, disappear with dismaying swiftness. When conditions are just right, it seems that every family in the Front Range region turns up at the park to enjoy the sights and sounds along the lower reaches of the renowned Trail Ridge Road (U.S. 34), which stretches 48 curvy miles between Estes Park on the east and Grand Lake on the west.
Visit this site for additional information about Rocky Mountain fall foliage viewing.
The fall colors in Montana's Glacier National Park will delight visitors as usual this year, but windshield tourists do need to be aware of access limitations made necessary by the Going to the Sun Road rehabilitation project. Logan Pass will be closed to through traffic on September 20 to allow accelerated work on the Sun Road. East side traffic will still be able to access Logan Pass and popular hikes (including Highline, Hidden Lake Overlook, Piegan Pass, and Siyeh Pass). At Glacier, autumn color starts in the subalpine zone by early September with vibrant orange Rocky Mountain maple, and red and orange vaccinium (huckleberries, whortleberries), etc. In mid- to late-September and even into early October the color moves into lower elevations, yielding gorgeous yellow, gold, and orange birch, cottonwood, aspen at mid-elevations. Golden swaths and archways of Western larch peak in mid- to late October along roadways (almost a golden halo along the U.S Highway 2 corridor and Middle Fork of the Flathead River) and the park's lake corridors, especially the North Fork lakes (including Kintla and Bowman Lake).
Like Rocky Mountain and Glacier, Wyoming's Grand Teton National Park and the contiguous John D. Rockefeller, Jr. Memorial Parkway have a short, but spectacular fall color season centered on gloriously golden aspen groves that peak in mid- to late September. Grand Teton's Jenny Lake area is a renowned destination. Access the one-way Jenny Lake Scenic Drive, which skirts the northeast shore of the lake and offers spectacular views of the peaks and colors, by driving south at the North Jenny Lake Junction (just south of String Lake). The Teton Park Road, which follows the base of the Teton Range from Moose Junction north to Jackson Lake Junction, offers lots of color. For more color and panoramic views of the Teton Range, Jackson Hole, and Jackson Lake, take the Signal Mountain Summit Road, which roughly parallels the Teton Park Road southeast of Jackson Lake and gains 800 feet in elevation.
In Washington's Mount Rainier National Park, the main sources of fall color are vine maple, huckleberry bushes, cottonwood, mountain ash, willow, elderberry, aspen, and tamarack. The leaves begin coloring up in early September. If you hit the leaves at their peak (usually late September to early October), driving on State Route 410 through Chinook Pass or on the White Pass Scenic Byway (U.S. 12) will be a truly memorable experience. In the Chinook Pass and White Pass areas, you can still see gloriously golden tamarack (western larch) when the serious snow begins to fall in November. Since disruptive snowfalls can occur even earlier than that in these mountains, Rainier leaf peepers need to be careful weather watchers.
Some Other Western Parks to Consider
Several dozen other west-of-the-Mississippi NPS units, mostly highland or mountain parks, have scenic drives that offer fall colors as a seasonal bonus. Three that come to mind in this context are Zion National Park, Canyon de Chelly National Monument, and Sequoia National Park.
Located just a three-hour drive northeast of Las Vegas, southern Utah's Zion National Park has some of the best fall color of any western park. And because of the large size of the park (146,598 acres) and the great variety of elevations, exposures, and microclimates, the season can last as long as four months. The first color show of the fall occurs near Lava Point, one of the highest places in the park (elev. 7,890 ft.). There in the high country of the Kolob Terrace, the aspen groves that sprawl across the plateaus turn golden yellow by mid-September. For this early show, and the spectacular panoramic view from Lava Point, take the Kolob Terrace Road to the Lava Point Road. Since Zion has an abundance of deciduous trees (aspen, cottonwood, bigtooth maple, box elder, ash, etc.) and bushes, vivid displays of red, gold, and flaming orange adorn various areas of the park as the season progresses. In lower, warmer parts of the park, where the color typically peaks in late October or early November, some areas may show good color into December.
Situated on a huge Navajo Indian Reservation in the Four Corners region of northeastern Arizona, Canyon de Chelly National Monument does not normally leap to mind when you think of fall foliage, but you shouldn't dismiss it out of hand. The park's abundant aspens and cottonwoods turn gloriously gold and yellow here by late October, and the blend of brilliant foliage and colorful cliffs is especially pleasing. Scenic drives from the visitor center and along the canyon rim lead to ten overlooks (three on the North Rim Drive and seven on the South Rim Drive) providing excellent views of the canyon below.
Yes, you can enjoy fall colors in southern California too. In Sequoia National Park, the Generals Highway, which links to Highway 198 and blends almost seamlessly into California Hwy 180 in Kings Canyon National Park, begins at the Foothills Visitor Center (elev. 1,700 feet) and winds through rugged terrain adorned with colorful foliage. Steep grades (5-8%) beg caution and argue against large RVs.