John Forrest Dillon served as a lecturer at the University of Iowa College of Law during his time in law practice. He came to Iowa to study medicine, graduating from the University of Iowa College of Medicine in 1850. Thereafter, he read law in Iowa and was admitted to the Iowa bar in 1852. He was elected to a judgeship in Iowa state court in 1858, and was elevated to the Iowa Supreme Court in 1862.
Judge Dillon was appointed to a federal Circuit Court judgeship in the Eighth Circuit by President Ulysses Grant in 1869. After resigning his federal judgeship, he taught law at Columbia Law School and Yale Law School. Judge Dillon left a sizable bequest to the University of Iowa College of Law in 1914, providing scholarships for Iowa law students.