Historical Photo of the Month - August 2007

Bailey Bridge
Photograph Number JB-2045B

In 1942, the first wooden footbridge was built over the Arroyo Seco, providing access to an unpaved parking area that would later be known as the "East Lot". The bridge was washed away after heavy rains in 1943, and the small bridge shown on the left in this photo was soon built to replace it. By the mid 1950s the parking lot had been enlarged and paved to accommodate the Lab's increasing population, and a larger bridge was needed.

In 1956, E.M. Pierce of JPL Plant Services suggested using an Army surplus "Bailey" bridge to span the arroyo. Bailey bridges were developed during World War II by Sir Donald Bailey to enable bridges of varying spans and carrying capacities to be quickly erected by unskilled manual labor. The basic components were standardized and interchangeable.

Approval was needed from L.A. County Flood Control and from the City of Pasadena, which leases the land to JPL. Many rules and regulations had to be followed, such as "This bridge is never to be used for vehicular traffic except in cases of extreme emergency; and except for guards and service vehicles ...." It also had to have sufficient clearance above the bridle trail in the arroyo, so that a rearing horse would not hit its head (or the rider's head). The design was finally approved, parts were ordered, and a JPL construction crew assembled the two 130 foot spans in 1958. The bridge was located between buildings 121 and 11, with a guard shelter next to it.

The Bailey bridge was later opened to one way traffic, but the transportation needs of JPL again grew larger than the capacity of the bridge. In 1972, the current east lot bridge was built, with two-way traffic and a raised pedestrian walkway. The larger bridge was able to allow access by large fire trucks and buses which carry employees from the parking lot into JPL. The wooden bridge and Bailey bridge were dismantled.

[Archival sources: Photo albums and indexes, various Lab-Oratory articles. Information about Bailey bridges was found on various web sites.] For more information about the history of JPL, contact the JPL Archives for assistance.