Places to see a Blackbird on display include:

Multiple variants:
National Museum of the United States Air Force at Wright-Patterson Air Force Base, near Dayton, Ohio (an SR-71A, YF-12A and M-21/D-21 drone)
March Field Air Museum, Riverside, California (an SR-71A and a D-21 Drone)
SR-71A variant:
Air Force Armament Museum, Eglin Air Force Base, Florida
Air Force Flight Test Center Museum, Edwards Air Force Base, California
Air Force Plant 42 Production Flight Test Installation, Palmdale, California
American Air Museum in Britain at the Imperial War Museum, Duxford, Cambridgeshire, England (the only example displayed outside the US)
Barksdale Air Force Base, Bossier City, Louisiana
Beale Air Force Base, Marysville, California
Castle Air Museum, Atwater, California
Evergreen Aviation Museum, McMinnville, Oregon
Kansas Cosmosphere and Space Center in Hutchinson, Kansas
Lackland Air Force Base, San Antonio, Texas
March Field Air Museum, Riverside, California
Museum of Aviation, Warner Robins, Georgia
Pima Air & Space Museum, Tucson, Arizona
Steven F. Udvar-Hazy Center, at Washington Dulles International Airport in Chantilly, Virginia
Strategic Air and Space Museum in Ashland, Nebraska
Virginia Aviation Museum in Richmond, Virginia
SR-71B variant:
Kalamazoo Aviation History Museum, Kalamazoo, Michigan
SR-71C variant:
Hill Air Force Base Museum, Ogden, Utah