Prior to the advent of the Internet, scanner code books served as the primary method for obtaining scanner frequencies. The dozens of websites dedicated to this specific interest make the information readily available.
Most websites dedicated to the subject have a wide and diverse variety of frequencies available across a full range of emergency services such as fire, ambulance and police. Many sites sort the information regionally and offer an interface where you click on your state and access a full range of relevant frequencies. Purchase scanner code books through electronic stores and online retailers. Code books offer an alternative resource.