Business Loop I-5 - Chehalis and Centralia

This route of Business Loop I-5 originally started at Exit 76 in Chehalis. It followed Parkland Drive and SW 13th Street to Market Boulevard (old U.S. 99) through the city of Chehalis. The historic alignment of U.S. 99 represented the business route north to Centralia, where Main Street west and Harrison Avenue north returned the loop to I-5 at Exit 82.

The route of Interstate 5 between Exits 78 and 102 was completed as a new alignment for U.S. 99 in the early to mid 1950s. This included construction of the National Avenue Extension, an east-west connector linking U.S. 99 on National Avenue in Chehalis with the freeway leading north to Centralia. The connector was temporarily a part of U.S. 99 until the eventual I-5 opened southward from Exit 79 to near Exit 52 within the vicinity of the Toutle River.

Mark Bozanich further added from an email sent on June 1, 1999:

When Interstate Business Loops were posted in Washington State in the mid-late 1960s, not only was old U.S. 99 from the south end of Chehalis to Exit 82 in Centralia posted as Business Loop I-5, but the National Avenue Extension (Chamber Way) was posted as Business Loop I-5 as well. This provided a way to use Business Loop I-5 to approach downtown Chehalis from the north without going all the way through downtown Centralia.

The National Avenue Extension was renamed Chamber of Commerce Way by the late 1990s. The route remained part of the Business Loop system for I-5, acting as a spur between the freeway mainline and National Avenue portion of old U.S. 99. Shields for Business Loop I-5 were still posted on Chamber Way in early 1999. One marker stands eastbound at State Avenue as of 2014.