There are 7 US Post Offices in Lincoln County serving a total of 19,687 residents equating to 2,812 residents per post office. It's estimated that approximately 31,423 packages are handled across the 7 county post offices annually. Lincoln County is a county located in the U.S. state of Montana. As of the 2010 census, the population was 19,687. Its county seat is Libby. The county was founded in 1909 and named for President Abraham Lincoln. This heavily wooded and mountainous county once was part of Flathead County until residents of Libby and Eureka petitioned the state legislature for separation. Libby won an election over Eureka to host the county seat."