Major Columbus power supplier American Municipal Power, Inc. will soon lose its leader of two decades. Marc Gerken will retire as president and CEO of the Columbus nonprofit next year. He took on those roles in 2000 for the 170-employee company, which supplies power and services to 135 municipal electric systems and 650,000 customers in Ohio and eight other states. "I am honored to have led this organization for 20 years, and to have worked alongside my colleagues who impress me every day,"...