Constructed in 1869, the Pioneer Courthouse is the oldest federal building that still stands today in the Pacific Northwest. It is a federal courthouse, but is also known as the Pioneer Post Office, because the agency was once located inside the building until 2005.

The Pioneer Courthouse is a historic site, declared as a National Historic Landmark in 1977 and was listed in the National Register of Historic Places in 1973. It was initially called the United States Building, and was first used by Judge Matthew Deady in 1875.

The Pioneer Courthouse survived a series of demolition threats in the past. It was last restored in 2005, including some additions to make the building earthquake-proof, as well as giving room to a secure parking lot for judges in the basement.