Emlin McClain graduated with a legal degree from University of Iowa in 1873. He practiced law in Des Moines until 1881, when he became a professor at the law school. He was the first Iowa law professor to have also graduated from the University of Iowa College of Law. He led the movement to expand the required course of study from two to three years. He also served as a compiler and editor of Iowa's state codes.
In 1887, he became Vice-Chancellor of the law department at University of Iowa, under Chancellor James M. Love. He served as Chancellor from 1890 to 1900, when he was elected to the Iowa Supreme Court. He served on the bench until 1912, spending two years as Chief Justice. After retiring from the Supreme Court, he taught law at Stanford University, before returning to Iowa in 1914 to serve as dean of the law school. He died in 1915.