Entrepreneurs and businesses are capitalizing on the eclipse mania that's spreading across the U.S. Millions are expected to travel to the 12 states, from Oregon to South Carolina, where the total solar eclipse will be visible on August 21. Some businesses, notably hotels in the eclipse's "path of totality," where the moon will completely block out the sun, are raising prices. Others elsewhere are using it as a marketing opportunity.

Madras, Oregon, which has a population of around 6,000, is expecting 100,000 visitors, according to reports. Nick Bowlby, owner of Charlie's O.K., the only barbershop in town, says businesses eagerly await the crowds. "I would not describe it as panic; it's mania," he says.

Bowlby ordered 60 beer kegs and transformed the vacant lot next to his shop into an outdoor beer garden with four food trucks ahead of the three-day population boom. "I have no idea how much money we'll make or what to expect," he says. "But we'll do well. It's like an outdoor BBQ joint in Brooklyn."

Nashville, Tennessee, which lies in the eclipse's path, expects 75,000 visitors. Every hotel is booked through August 21, says Heather Middleton, who runs public relations for Nashville's "Music City Solar Eclipse" marketing campaign.

"The city will be full on Sunday night," says Middleton. "We are at 100 percent occupancy."

Most hotels in the eclipse's path have been booked for years, the AP reports, and many are charging five times the usual rates. Oregon's Department of Justice warned that hotels across the state were illegally price gouging customers.

The Suttle Lodge, a one-year old lake resort in Oregon's Deschutes National Forest, is hosting a free music festival with Chris Funk of Portland-based indie band The Decemberists, says Donald Kenney, a partner and manager of the cabin resort. "We want to spread the gospel of our property to more people and hopefully get on people's travel check lists," he says.

Warby Parker, the venture-back eyeglass maker, is also using the eclipse as a marketing opportunity. On August 1, Warby Parker will start giving away paper eclipse glasses, which are designed to safely view the event, at its stores. It's also hosting a contest and will fly one lucky winner, plus a guest, to its Nashville headquarters for an eclipse-viewing party.

Entrepreneurs have long recognized celestial events as a business opportunity, according David Baron, author of recently published American Eclipse (2017, Liveright), which chronicles the national excitement over the 1878 total solar eclipse.

Hotels in Denver and Wyoming were filled to capacity, with some guests sleeping on billiards tables and in dining rooms, he says. Enterprising newsboys made "eclipse glasses" by smoking glass lenses over fire to darken them. Even pick-pockets traveled from New York to take advantage of crowds in Denver, he says.

"Fundamentally, it's the same experience; people are giddy with excitement for an event that connects us to celestial affairs that are beyond our day-to-day life," says Baron.