Dr. Dennis Miller was born in Minden, Louisiana, in 1866. He lived there until 1875 when he and his family moved west and settled in Plano. The Millers traveled by covered wagon, and Dr. Miller later told his family that he walked most of the way. Dr. Miller attended the Plano Institute, an early school in Plano.

After graduation, Dr. Miller left for the Baltimore School of Medicine in Baltimore, Md., graduating in 1890. This school is now known at Johns Hopkins School of Medicine. During this time, Dr. Miller also taught school to help defray medical school costs. He was certified as a first grade teacher during the years 1887 and 1888.Dr. Miller began practicing medicine in Lebanon, Texas, near what is now Frisco. Within a month, he moved to Murphy and established his home and his practice. He married Rebecca Olinger and they had two daughters. After Rebecca's death, Dr. Miller married Ruth Rossiter. She and Dr. Miller had five daughters.Dr. Miller either walked, rode horseback, rode in a buggy, or rode his bicycle whenever he made house calls. He eventually bought a car, possibly the first in Murphy and continued to attend to Murphy's medical needs until 1935. He was a gentle, kind man with sky blue eyes. He wrote poetry about nature, his family, and his faith.