Brookhart was born in a cabin on a farm in Scotland County, Missouri, the son of Abram C. and Cynthia Wildman Brookhart. He was educated in country schools, graduated from Bloomfield High School, and attended Southern Iowa Normal School, both in Bloomfield, Iowa, where he graduated in 1889 with an emphasis in scientific courses. For five years, he taught in country schools and high school while h studied law in offices in Bloomfield and Keosauqua, Iowa. He was admitted to the bar in 1892 and began practice in Washington, Iowa. Four years later, his brother, J. L. Brookhart, joined his firm. He served for six years as Washington County Attorney.