This old court house sitting right on Route 66 is full of history. It is currently used as the Holbrook city offices and the a visitors' center. The museum is packed with photographs, tools, furniture and other relics of past inhabitants of the area. Most fascinating of all, perhaps, is the old jail, which you can enter and examine the artwork (some of it highly skilled) left by its former inmates.
If you go:
Admission is free, but donations are welcomed, and will get you a free piece of petrified wood to take home. Be sure to watch the film in the auditorium, as it discusses the ghosts of former jail inmates that supposedly haunt the building.
Links:

100 East Arizona Street
Holbrook, Arizona 86025 USA
Holbrook@GoTourAZ.com
Phone Numbers:
Chamber of Commerce
+1 (928) 524-6558
+1 (928) 524-6558
Toll Free Information
+1 (800) 524-2459
+1 (800) 524-2459