The allusion to William Jennings Bryan is made in Chapter 16 of To Kill a Mockingbird after people from the other end of the county pass by the Finch house followed by Mr. Dolphus Raymond astride his thoroughbred. Then, a wagon full of Mennonites, "women wearing sunbonnets and dresses with long sleeves as a bearded man in a wool hat" drove. Another man is on a mule. When a wagonload of stern-looking passed they pointed to Miss Maudie and called out an ominous verse of the Bible. When Jem asks her if she is going to court, Miss Maudie replies, "I am not....it's like a Roman carnival."
Miss Stephanie Crawford walks up and says, "um, um, um, ...Look at all those folks; you'd think William Jennings Bryan was speakin'."
William Jennings Bryan (1860-1920) was a famous politician and lawyer, nominated three times for president by the Democratic Party. His speeches were characterized by power and drama and drew large crowds, especially in the South. Of particular note is his famous "Gold Cross" speech about the issue of whether to endorse the free coinage of silver at a ratio of silver to gold of 16 to 1. Jennings employed much rhetoric in his dramatic deliveries and aroused crowds to near frenzies. Here is the last part of the "Gold Cross" speech:
Having behind us the commercial interests and the laboring interests and all the toiling masses, we shall answer their demands for a gold standard by saying to them, you shall not press down upon the brow of labor this crown of thorns. You shall not crucify mankind upon a cross of gold.
Because Jennings drew crowds from miles around the area where he appeared, crowds that were excited in their anticipations of hearing him, Miss Stephanie draws the comparison between the arrival of almost everyone in the county with those audiences of Jennings.