Sandburg paved the way for what we now recognize to be the style of Beat poetry. His simplicity, poignancy, and language of the people made his sort of poetry perfect for the tell-it-like-it-is approach we saw later in the 1940s and '50s in America.
His work isn't dressed up with fancy words or allusions that only academics can recognize. And although this earned him quite a bit of criticism from some literary juggernauts, the people who enjoy his work appreciate his style that continues to inspire artists today. Heck, there are even a bunch of schools and parks named after the guy. Who needs critics when you can have a park?
So, if you dig his cut to the chase vision in "Fog," you'll likely see more of it in his other works.