In addition to the number of circuit judges authorized under Section 2 or Section 2a, whichever number is greater, one additional circuit judge shall be elected in each circuit, other than Cook County, having a population of 230,000 or more inhabitants in which there is included a county containing a population of 200,000 or more inhabitants and in which circuit there is situated one or more State colleges or universities and one or more State Mental Health Institutions and two or more State Institutions for Juvenile Offenders under the authority of the Illinois Department of Juvenile Justice, each of which institutions has been in existence for more than 20 years on the effective date of this amendatory Act of 1970.