Mydland attended South Dakota State University for a Bachelor of Science degree, and the University of South Dakota for his Bachelor of Laws degree.
He also served in the United States Navy during World World War II, from 1943 to 1946. Prior to his election to the state senate, he was the County Attorney for Brookings County, South Dakota. He served in the South Dakota State Senate from 1963 to 1968 representing the 13th district (1963-1966) and the 6th district (1967-1968).
He was also Attorney General of South Dakota from 1969 to 1973.
He was later a judge on the South Dakota Third Judicial Circuit. In religion, he is Lutheran.
Member South Dakot Code Compilation Commission, 1964-1968. Member South Dakot Planning and Advisory Commission Crime and Juvenile Delinquency, 1970-1972. Advising committee South Dakot Alcohol Safety Action Project, 1971-1972.
Served with United States Naval Reserve, 1943-1946. Member American Legion.
Married Lorrie Grange, May 29, 1958. 1 child, Gabriel.