According to Robinson, the fictional town of Gilead (Gilead means 'hill of testimony' in the Bible – Genesis 31:21) is based on the real town of Tabor, Iowa, located in the southwest corner of the state and well known for its importance in the abolition movement. Likewise, the character of the narrator's grandfather is loosely based on the real life story of the Rev. John Todd, a congregationalist minister from Tabor who was a conductor on the Underground Railroad, and who stored weapons, supplies and ammunition used by abolitionist John Brown in his "invasion" of Missouri in 1857 to free a group of slaves, and later—without Todd’s knowledge or involvement—in his 1859 raid on the U.S. military arsenal at Harpers Ferry, West Virginia. Robinson talks about Ames's grandfather's involvement in the civil war. She mentions an illness known as 'camp fever'. The term was generally used to describe Typho-malarial fever. Symptoms included: pronounced chills followed by fever, abdominal tenderness, nausea, general debility, diarrhea, retention of urine, and furring of the tongue. Also, as John Ames was describing his sermons in his letter, he tells his son that there was one he had burned before he was supposed to preach it. This sermon was written around the time of the Spanish Influenza.
Regarding Robinson's theological influences in Gilead, she herself has explained the importance of primary Calvinist texts, particularly Calvin's Institutes of the Christian Religion. In regard to Calvin’s Institutes, Robinson states in her Yves Simone lecture entitled "The Freedom of a Christian," that “one of the reasons these texts are important to me is because they have everything to do with my own theology certainly, with my aesthetic perhaps, and in so far as I can say I have an intention in writing, they have everything to do with my intention.”.