See Maps of Where Eclipse Seekers Flocked and the Traffic That Followed

Monday’s solar eclipse drew huge crowds to the path of totality, temporarily ballooning the populations of small towns and rural areas across the country. The map above shows an estimate of where human activity increased the most on Monday, compared with that on an average Monday, according to data from Mapbox, an online mapping company.

Some towns in the path of totality expected their populations to double, and the data — drawn from mobile-device activity — showed such increases in many places.

Among the towns with more than 100 percent increases in activity were St. Johnsbury, Vt.; Lancaster, N.H.; and Ste. Geneviève, Mo. State parks like the Adirondack Park in New York and many areas in the Ozarks region of Arkansas and Missouri were also popular destinations. The data includes activity for the entire day and also shows a pattern of movement away from the path of totality, as seen in the darker areas on the edges of the path in the map above.

Around midafternoon Monday came the main event: the moment of totality, when the moon moved fully in front of the sun, turning daylight to darkness. That climax lasted only a few minutes, and then eclipse watchers started their trips home or to hotels.

Traffic was stopped or delayed along some highways more than eight hours later, according to data from TomTom, a mapping and navigation company. Officials in many parts of the country had warned of snarled traffic, and roads in the Northeast — from New York to Maine — had the greatest concentration of hourslong delays.

Interstate 87 in New York had a line of traffic more than 55 miles long around 6 p.m., and cars were still backed up for miles at 11 p.m. on Interstate 93 in New Hampshire, more than seven hours after the eclipse, according to TomTom.

On a normal weekday afternoon, the 210-mile drive from Burlington, Vt., to Somerville, Mass., takes about three and a half hours. On Monday, the same trip took Liam Sullivan, 26, of Somerville, more than nine hours after watching the eclipse.

“The worst part was that in the first four hours we only went about 40 miles,” Mr. Sullivan said. “A solid marathoner is beating our pace there. It was completely hopeless congestion the entire time.”

While drivers in the Northeast faced the worst of the delays, there were also long traffic jams outside of Indianapolis, St. Louis and Columbus, Ohio.

“It was definitely the worst traffic I’ve ever seen in my life,” said Richard Chen, who spent nine hours driving from Newport, Vt. to his home in Brooklyn, N.Y., after the eclipse.

Despite the traffic, Mr. Chen said he didn’t see any road rage. “I think people were just kind of thrilled to witness the eclipse, and the traffic and road tripping was just part of the experience,” he said.

Was the drive worth it? For Mr. Chen, there was no question. “Definitely,” he said, noting that the next major U.S. eclipse will take place in 2045.

Mr. Sullivan wasn’t so sure. He said that the eclipse was stunning and that he was grateful to witness it but added: “If you told me yesterday how long it would take, I would have gone back to bed.”