National Register of Historic Places in Napa County
This stone arch bridge measures 169 feet long and about 26 feet wide. It has five spans. The center span and the one adjacent on the east are 40 feet long; the others are 20 feet long. The bridge is constructed of locally quarried rock, probably trachytic tuff.
Stone masonry bridges are rare in California. Their construction was limited primarily to Napa County, and most of the examples once there have disappeared.
The bridge is especially notable as remnant of Napa County's bridge-building program in the early 20th century. Because of its length, the Milliken Creek Bridge was an unusually ambitious project. Most of the county's stone masonry bridges were less than half as long.
Today the bridge is one of the two or three longest unaltered stone masonry bridges in California.
Source: NRHP nomination form.
Ten Threatened Treasures in Napa County
This property was on a list of ten threatened historic properties compiled in 2015 by Napa County Landmarks:
The Stone Bridges of Napa County