What is the WPA, and why won't Mr. Cunningham work for it? What does this reveal about his character?

The WPA was the Works Progress Administration, a work program implemented to create jobs and complete public works projects. Mr. Cunningham won't work for the WPA because it would mean he'd have to neglect his land, and also because he would be aligning himself politically if he did so. Cunningham was independent and unwilling to compromise his own beliefs in order to make money.

If he held his mouth right, Mr. Cunningham could get a WPA job, but his land would go to ruin if he left it, and
he was willing to go hungry to keep his land and vote as he pleased. Mr. Cunningham, said Atticus, came from a set breed of men.