There are 6 US Post Offices in Clark County serving a total of 6,023 residents equating to 1,004 residents per post office. It's estimated that approximately 9,613 packages are handled across the 6 county post offices annually. Clark County is a county located in the U.S. state of Missouri. As of the 2010 census, the county's population was 7,139. Its county seat is Kahoka. The county was organized December 16, 1836 and named for William Clark, leader of the Lewis and Clark Expedition and later Governor of Missouri Territory. Clark County is part of the Fort Madison\u2013Keokuk, IA-IL-MO Micropolitan Statistical Area."