this is about the biggest advertising vehicle I've ever seen

The Rexall Train, a promotional 12-car streamlined and air-conditioned train, 1936

https://www.flickr.com/photos/27862259@N02/7875235800/

"The Depression is over!", declared Louis Liggett. And with that, he put the most fantastic promotional train ever conceived on the rails to the four corners of the nation because he wished to host a national convention for druggists (pharmacists) across the country. Realizing, however, that financial struggles would likely see low turnout at a central location Liggett came up with the radical idea of hosting a rolling convention by rail.

From March to November 1936, the 12-car streamlined, air-conditioned billboard-on-wheels toured the length and breadth of the United States.

The tour made its way from Boston through the Midwest, Southwest, and north up the Pacific coast. Zigzagging across Canada and the US Northwest, the train descended into Chicago for a 3-week refurbishment half way through its tour. Back to the east coast it went before heading south, west, southeast, and north again -- finishing up on November 24, 1936 in Atlanta, GA. In the end, the train visited every state except Nevada.

Final tally: 29,000 miles, 47 states and Canada, 10,000 druggists and 20,000 Rexall salespersons, 2.3 million visitors for the Million Dollar Rexall Streamlined Train.

The NYC railroad was also the first to streamlined a steam locomotive in 1934, the Commodore Vanderbilt. This was the inspiration for #2873, which received an almost identical shrouding.

The consist included twelve heavyweight Pullman cars, completely overhauled and given a streamlined look to make the train really standout. Each car received a new roof and diaphragms that made the train the longest 'streamlined' train yet fielded.

 What was dubbed "The Million Dollar Rexall Streamlined Convention Train" featured a livery of blue and white, Rexall's corporate colors. The entire consist was very well planned and coordinated: all twelve cars were named for the latest Rexall products with some open to the public as exhibitions; the other seven were either private or available only to druggists and store owners. To further enhance its appeal the train was entirely air-conditioned.

The front half of the train was planned for public exhibition. To that end, four Pullman cars were outfitted with displays of virtually every product Rexall offered. The hottest products lent their names to the cars of the train. Kantleek, Firstaid, Ad-Vantages, Research, Bisma-Rex, Cara Nome, and six other star-product names adorned on the sides of the cars.

In 109 cities the train was scheduled to host druggists' conventions. This is where the next four Pullmans came in handy. The Klenzo, Symphony, Adrienne, and Mi-31 were all converted to the standards of a topnotch convention hotel. Klenzo and Adrienne were lecture cars connected by a PA system. Between them was the dining car Symphony -- suited for serving hundreds of conventioneers a mouthwatering buffet lunch or dinner anytime, anywhere. (Pullman had provided three master chefs.) After a day of seminars, the Mi-31 offered two bars and a lounge area for relaxation.

Found on https://www.facebook.com/HeritageRailway?fref=nf
and  http://www.themetrains.com/rexall-train-main.htm