Transcript for Nation gears up for greatest cosmic light show on Earth

Finally tonight here, the test coming for so many small American towns. Are they ready for the crowds for the great American eclipse? David Wright from Wyoming. Reporter: In central Oregon, the traffic jam has already started. This is all Heang into town. Reporter: This one stretching 15 miles. There's a run on the gas stations too, ahead of Monday's eclipse. Fully one-third of the country is within driving distance of the path of totality. Colorado highways already carry "Heavy eclipse traffic" warnings -- this is glendo, Wyoming, population 205. The closest spot to Denver in the center line of totality. They're expecting 100-thousand people because this is one of the closest spots to the city of Denver. So glendo now has one-to-one ratio of porta-potties to people. No hotel rooms here. Eclipse chasers will watch and camp in this field, the local airstrip. So this is glendo international airport? Yes. Exy. Reporter: Proper eclipse dplass in short supply too. The nation gearing up for the greatest cosmic light show on Earth. David Wright, ABC news, glendo, Wyoming. Set your DVRs. 1:00 P.M. From Boston's news later,

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