In 1913 Chicago businessman and inventor Magnus Hendrickson started building hard-working trucks to which he attached his family name. According to the history on the company website, “In 1926, Hendrickson introduced the first tandem truck suspension, which mounted the axles on each end of an equalizing beam. This unique ‘walking beam’ design distributed the truck’s load evenly between the two rear axles, which improved traction and greatly reduced the effects of bumps and potholes in the road.” Over the years, Hendrickson would be sold, focus on suspension components and truck production was discontinued. Here’s a video of a 1966 Hendrickson BD425 that appeared at last summer’s Trucker’s Jamboree in Iowa.