Three Chicago museums will offer free access to Illinoisans over the long Martin Luther King Junior holiday weekend. The Shedd Aquarium, Adler Planetarium and Field Museum will allow patrons to visit free of charge. All that’s needed is a valid ID or proof of residency. The Shedd Aquarium is free today through Monday. The Adler is free Monday through Wednesday. The Field Museum will be at no charge Monday and January 22nd and 29th.