How ya gonna keep em on down on the farm after they've seen Paree?

The post World War I hit song, about the changed expectations of the returning soldiers, raised a profound question for the anti-change "Main Street," depicted by Sinclair Lewis in his great novel of that era.  But what happend "over there" that changed people?  One remarkable story was found in Paris Noir, by Tyler Stovall on the Washington Post website, relating to African American soldiers, who were relegated to menial tasks but astounded everyone by carrying them out in a superlative manner.  Here's a part of the story:

In contrast to the poor opinions the army leadership expressed about their abilities, black laborers in France often performed impressive physical feats, especially black longshoremen. To an important extent port workers formed the linchpin of the entire American military effort in France. The United States Army had never before fought such an extensive campaign so far away from home. Unloading and deploying both soldiers and war material in French ports had to be done as quickly and efficiently as possible in order to ensure an Allied victory. By the middle of 1918, large numbers of black longshoremen were busy unloading American ships in French harbors like Brest, Saint-Nazaire, and Bordeaux. Many of these workers had never even seen a ship before coming to France, much less worked on one, and yet their accomplishments frequently astonished French and white American observers alike. One compared their speed to that of Noah loading the Ark, and another commented, "They are the finest workers you ever saw. One Negro can do four times as much work as any other man, and have fun doing it. The French stevedores stand by and watch with amazement at my hustling gangs. The way they handle a 100-pound crate makes the Frenchman's eyes bulge." In one instance, African American longshoremen unloaded five thousand tons of material in one day, when French officials had estimated that six thousand could only be moved over an entire month. During the month of September 1918, black stevedores set a record by unloading an incredible twenty-five thousand tons of cargo per day for several weeks.

These achievements are astounding -- the question I'd like to pose is: what is it about agricultural work that the men brought to this new task and that allowed them to excel?  At any rate, what we do know is that when they got back, they were intolerant of abuse on the farm and many moved to the cities.  Jacob Lawrence's magnificent paintings of the Great Migration, recently shown in their entirety at MoMA offer a way of understanding the decision that people made to go to the cities and start a new life.  That is a major story of Main Street, at least as Sinclair Lewis sees it.