A mighty darkness is about to descend upon the land, and sky watchers couldn't be more thrilled.
On Aug. 21 the Earth, sun and moon will blow our minds during a total solar eclipse that will last a little more than an hour and 33 minutes, coast to coast.
The celestial bodies will line up to block the sun from view, an event scientists and historians are calling the Great American Eclipse.
Here's why all the excitement: This total eclipse of the sun is the first since 1776 whose path of totality — the narrow corridor where observers will be in the moon's shadow as it covers the sun — lies completely within the continental United States and no other country.
Millions live within a day's drive of the 70-mile-wide umbra, or shadow path, that will stretch diagonally through 12 states, from Oregon to South Carolina. Alas, it won't touch California, but that doesn't mean residents of the Golden State can't be part of it.
Partial eclipses happen all the time, but this rare cosmic occurrence will turn the summer day dark, reveal stars in the daytime sky and move the black disk of the moon to where the sun should be.
Along the horizon, twilight will glow in sunset colors and the temperature will drop suddenly. Fans liken a total solar eclipse to a spiritual experience, while other experts describe it in poetic terms.
"For a couple of minutes, it feels like you are standing on an alien planet because everything around you looks so different from normal reality," said Michael Zeiler, a professional cartographer and amateur astronomer in Santa Fe, N.M.
"The most beautiful object in the sky, which is invisible for all of our lives, is revealed for a precious two minutes, and that's the sun's corona. It's incredibly beautiful. This is your only chance to see it."
Zeiler and his wife, Polly White, spent the last three years preparing for the event, pouring knowledge into their website, GreatAmericanEclipse.com. He has developed an app, available at the website, that highlights festivals, travel routes and lodging.
Although the best hotel options have long been sold out and crowds and traffic are expected all along the path of totality, Zeiler emphasized that this eclipse covers much of the sparsely populated West, whose allure includes clean air, clear skies and uncrowded highways (the better to chase the best weather).
He urged travelers to consider spending a few summer nights under the stars.
"Some people in the city have never really gotten a good view of the Milky Way and that in itself is an astonishing sight," he said.
"August is a wonderful time to grab a tent and sleeping bag and just go."
Here are some of the top places west of the Mississippi not to see the sun on Aug. 21.
Organized events include:
•A NASA official viewing site, Oregon SolarFest takes place Aug. 20 and 21 at the Jefferson County Fairgrounds to celebrate its premier eclipse-viewing location in Madras. The ticketed festival includes options for hot-air balloon and helicopter tours, rental camping gear, music, science displays, food and high-desert camping on the center line of totality.
•The Oregon Museum of Science and Industry Solar Eclipse Viewing Party at the Oregon State Fairgrounds (Aug. 21) in Salem.
•The five-day Oregon Star Party in the remote Ochoco National Forest.
•The multi-day Oregon Eclipse Festival near Mitchell, offering music, art, yoga and workshops.
The Idaho Falls area has the largest population within the path and will experience about 1 minute, 45 seconds of totality.
•The St. Anthony Sand Dunes offer 10,600 acres of white sand and camping within the path of totality.
•In Rexburg, Brigham Young University-Idaho is offering free reserved viewing areas, RV and bus parking and even boxed lunches to enjoy the 2 minutes, 20 seconds of total eclipse, one of the nation's longest.
•The Museum of Idaho, an official NASA eclipse-viewing site, will mount an exhibit about space and host speakers and films during eclipse weekend.
Serious sky watchers are heading to Wyoming's popular mountain resort areas and its wide-open spaces, clear skies and grand vistas of mountains and plains. Yellowstone National Park is just north of totality, but other areas are squarely within the shadow.
Viewing options include:
•In the week leading up to the cosmic spectacle, Casper hosts the Wyoming Eclipse Festival with historic tours, lectures and covered wagon rides.
•The centerline runs through the Jackson Hole Airport, Gros Ventre Road and Moose-Wilson Road, while the path of totality sweeps across the town of Jackson, Grand Teton National Park, Bridger-Teton National Forest, Jackson Hole Mountain Resort and Grand Targhee Resort. Most Jackson Hole hotel rooms are booked, but public parks in downtown Jackson offer good options for viewing, along with Phelps Lake in Grand Teton National Park and the park's Gros Ventre Campground, where sites are first-come, first-serve.
•Watch the eclipse from a high vantage point by climbing Jackson Hole-area peaks such as the Snow King Mountain in the town of Jackson or Static Peak in the Teton Range.
The highway allows great mobility if cloud-dodging is necessary, said Zeiler, adding that U.S. 385 near Alliance in western Nebraska offers uncrowded roads, proximity to maximum eclipse duration (2 minutes, 35 seconds) and good odds of clear skies.
•Lincoln, which offers nearly 5,000 guest rooms, is planning weekend events in Haymarket Park and easy access to the umbra's centerline.
•From Aug. 18 to 21, Alliance and nearby areas will offer a festival of music, arts and games, and on eclipse day, viewing areas at city parks, the rodeo grounds and Carhenge, a homage to Stonehenge made of automobiles.
•Stapleton, another desirable viewing site, is staging the Eclipse on the Range festival (Aug.16-21), featuring a craft fair, farmers' market, rodeo and an after-eclipse bash and beer garden.