Christy is organized around two primary groups of characters. The first group consists of the "foreigners," individuals who have traveled to Cutter's Gap, Tennessee, from the wider world to assist the mountain residents by enhancing their education, spiritual lives, and living standards. The protagonist, Christy Huddleston, is a nineteen-year-old who volunteers to teach at a school in the Eastern Tennessee mountains. Alice Henderson, a Quaker missionary, oversees Christy's efforts, providing the practical and spiritual support the young, inexperienced teacher requires. David Grantland is a young minister who arrives in Cutter's Gap and finds himself at odds with the local traditions and beliefs. Although Dr. Neil MacNeil was born and raised in the mountains, he has experienced life beyond and trained as a medical doctor. MacNeil returns to his birthplace to offer his medical expertise. While he connects with the mountain culture, he is eager to introduce the advantages of modern society to his community. MacNeil is aware of his unique position within the mountain society, representing both advanced education and the rich heritage he was born into. He strives to integrate the best aspects of both worlds within himself and others.

Cutter's Gap is home to several families, including the McHones, the McTeagues, the Aliens, the Becks, and the Spencers. Christy forms a special bond with Fairlight Spencer, the first adult she teaches to read in the community. In return, Fairlight helps Christy appreciate the natural wilderness's beauty and the folk wisdom and traditions of the mountains. Fairlight's unexpected death profoundly impacts Christy. Bird's Eye Taylor and his son Lundy represent the lawlessness and violence that have been unfortunate elements of life in the Ozarks. However, Bird's Eye Taylor's life illustrates how a person's innate gentleness can overcome the lure of societal violence.