Austin's new Circuit of the Americas announced that three-day general admission tickets for its inaugural grand prix in November have sold out.
US media reports said the venue estimates a whopping 120,000 spectators will attend on all three days of the race weekend.
"Worldwide fan interest has been remarkable," spokesman Geoff Moore said.
And the Austin American Statesman newspaper said the first layers of track asphalt have been laid, concrete for the corner curbs and pitwall poured, run-off gravel put down, and safety fencing is being installed.
Progress is also being made in Russia, despite earlier fears the resort city Sochi might not be ready for its inaugural 2014 race date.
Russian deputy prime minister Dmitry Kozak is quoted by the ITAR-TASS agency as saying the track will be ready for 2014, even though Sochi is also gearing up to host the winter Olympics.
"We'll be ready to host the first Russian grand prix in October 2014," he said in London.