Henry Markham was born and raised in a small farming community in upstate New York. He attended public school in Farmington, then Wheeler’s Academy in Vermont. Shortly after his graduation from the Academy in 1862, Markham and his brothers moved to Manitowoc, Wisconsin. According to his service records, he worked as a teacher until he enlisted in the army in 1863.
In 1864, Markham participated in General Sherman’s march to the sea. He was severely wounded at the battle of Whippy in 1865. He was discharged from the army in June that year. After the war, Markham returned to Wisconsin to study law and was admitted to the bar in 1867.
In response to an ad in the newspaper, Markham purchased a 23 acre ranch in Pasadena. In 1879, he, his wife and young daughter moved to Pasadena where Markham continued to practice law. Markham served on the school board and helped found the local public library. In addition, Markham was involved in a number of business ventures including part ownership in the Calico Union Mining Company.
Markham was a member of the U.S. House of Representatives from 1885 to 1887. He declined to be a candidate for re-nomination in 1886. During his campaign for Governor, Markham was referred to as "the dashing colonel from Pasadena." California suffered a depression during Markham's term. As a means to attract visitors and new residents to the state, he pressed for a Mid-Winter Exposition in 1894. The event, held in San Francisco, was a huge success.