The development was built in two phases, the names of which are reflected in the names of the two main mall buildings. Pioneer Place I, or The "Atrium Shops"/Zone A, opened in 1990 and was developed with assistance from the Portland Development Commission. Pioneer Place II, or The "Rotunda Shops"/Zone B, is located across Fourth Avenue to the east. Construction on Pioneer Place II began in 1998, and at the time was to add at a cost of around $60 million.