WOOD RIVER - Chestnut Health Systems was founded in 1973, and it wasn’t long before the organization became one of the largest providers of substance use, behavioral health and physical health treatments in the Riverbend region.Started in “a modest house” on West Chestnut Street in Bloomington, the small team worked with adults who were struggling with substance use disorders. Soon, Chestnut grew to meet other community needs, with the first sou…