Rockville is a former city in Delaware County, Iowa, United States. Bordering Dubuque County within the North Fork Township, it was approximately 3 miles northwest of Worthington and 1.5 miles west of t…Rockville is a former city in Delaware County, Iowa, United States. Bordering Dubuque County within the North Fork Township, it was approximately 3 miles northwest of Worthington and 1.5 miles west of today's Iowa Highway 136.