An advertisement brought to us by Paul Malon (who else?) on his Flickr photostream:
From the Greyhound official history: "1933. Greyhound is selected as the official transportation carrier at the 1933 Century of Progress World's Fair in Chicago. Taking a gamble on the success of the fair, the company reserves 2,000 hotel rooms and begins a campaign offering transportation and lodging to the fair on one ticket. The promotion earns more than $500,000 in Depression-era profits. "
Hemmings blog tells us about 60 so-called “trailer coaches” that Greyhound fielded for the 1933-1934 Chicago Century of Progress World’s Fair. They were the only motorized transport allowed on the grounds of the fair, and that they carried more than 20 million attendees throughout that time.
Here is "trailer coach" in front of the GMC pavilion. According to Don McKenzie @ ATHS Forum, GMC built these trucks for Greyhound (the badges on the hoods read “General Motors Truck”) on the T26 chassis using unique sheetmetal designed by the well known industrial designer James J. St. Croix.
As far as I know, these streamline tractor-trailer sets were local production, built in Chicago by Yellow Truck and Coach Manufacturing Company (a GMC division since 1925). We can call them spiritual predecessors of a much more famous public transit vehicle, the Model 719 aka Super Coach. And even considering all obvious differences we can't but mention that the 719 wasn't the first Yellow Coach/Greyhound streamliner.