After weeks of anticipation, the sight of the moon's shadow passing directly in front of the sun, blotting out all but the halo-like solar corona, will draw one of the largest audiences in human history, experts say.
When those watching via social and broadcast media are included, the spectacle will likely smash records.
Some 12 million people live in the 70-mile-wide (113-km-wide), 2,500-mile-long (4,000-km-long) zone where the total eclipse will appear on Monday. Millions of others have traveled to spots along the route to bask in its full glory.
Murphy, North Carolina, in the Smoky Mountains about two hours north of Atlanta, is among hundreds of small towns that are preparing for a huge influx of visitors.
"The weather forecast for Monday is beautiful, probably not a cloud in the sky all day," said Dave Vanderlaan, 61, a retired landscaper. "We're busy, but tomorrow anybody in Atlanta who says they want to see total, they're going to come up to this area, so it could be crazy."
The phenomenon will first appear at 10:15 a.m. PDT (1715 GMT) near Depoe Bay, Oregon. Some 94 minutes later, at 2:49 p.m. EDT (1849 GMT), totality will take its final bow near Charleston, South Carolina.
The "Great American Eclipse," as it is being called, will move diagonally across the country, northwest to southeast, providing a spectacular solar show -- again, weather permitting -- and an excellent excuse for scores of eclipse-viewing parties and music festivals.