The Marquam Bridge is a double-deck, steel-truss cantilever bridge that carries Interstate 5 traffic across the Willamette River from south of downtown Portland, Oregon, on the west side to the industrial area of inner Southeast on the east. It is the busiest bridge in Oregon, carrying 140,500 vehicles a day as of 2016. The upper deck carries northbound traffic; the lower deck carries southbound traffic. The Marquam also has on and off ramps for Interstate 405 on the south end of the bridge, while the terminus on the east bank of the river is near the interchange with Interstate 84. History Planning for the span started in 1956 as the last link in Oregon for the new Interstate Highway System for the main north-south route through the state. Even prior to construction, it was decided to name the span after Philip Marquam. Marquam was a state legislator and Multnomah County judge, who owned much of Marquam Hill where Oregon Health & Science University and the Veterans Affairs Medical Center now stand. Construction on the bridge's support piers began in January 1962. Construction on the bridge finished on February 28, 1966. The lower southbound deck was opened on October 4, 1966, and the upper northbound deck on October 18, 1966. The bridge was designed and built by the Oregon Department of Transportation at a cost of $14 million, equivalent to $ today. Funds for the project came from the Federal Highway Transportation Act. The bridge was redecked in 1983. In 1990, the approach lanes from both the east and west were widened to allow four lanes of traffic and an off-ramp to Water Avenue was built. Due to its importance, the Marquam was the first Portland bridge to undergo a seismic retrofit in 1995, which included installation of Italian made bearings add to the piers. Design The main span of the bridge is long and the two side spans are each for a total length of . Vertical clearance of the lower deck is and the upper deck is above the lower. The Marquam was designed by Ivan D. Merchant and Pieter Kiewit Sons Company served as the general contractor. At the eastern end of the bridge, on the lower deck, is a ramp stub which was intended to connect to the later abandoned Mount Hood Freeway project. The bridge was designed with four lanes in each direction. It was the