What does Miss Maudie mean when she says, "...we're making a step-it's just a baby step, but it's a step"? What evidence does she use to explain her optimism?

I think that she realizes that the town knows their shame. There is very little said about the trial after it is over.

*Ahem

She means that if more and more people start protecting black people, maybe the prejudice will stop and people will live in harmony, no matter their race and color. She is optimistic about things coming to an end and she knows that eventually all the racism will stop and Scout can walk hand in hand with a African American boy.