Lanark is a small unincorporated village located in Upper Saucon Township in Lehigh County, Pennsylvania. It is part of the Lehigh Valley, the third-largest metropolitan area in Pennsylvania. Residents of Lanark are served by the Center Valley and Coopersburg Post Offices with ZIP Code of 18034 and 18036, respectively. Lanark is located in Souther…Lanark is a small unincorporated village located in Upper Saucon Township in Lehigh County, Pennsylvania. It is part of the Lehigh Valley, the third-largest metropolitan area in Pennsylvania. Residents of Lanark are served by the Center Valley and Coopersburg Post Offices with ZIP Code of 18034 and 18036, respectively. Lanark is located in Southern Lehigh School District, and students in grades nine through twelve attend Southern Lehigh High School. The community was named after Lanark, Scotland.