To answer these questions for new businesses, established businesses, or for people working on a business plan, the St. Louis Public Library provides an online database called Standard Rate & Data Service (SRDS).
Most business depend on advertising to attract customers. SRDS provides data information for advertising through various media – mainly newspapers, radio stations, as well as television and cable operators. The data found in this database gives rates and demographic information by Designated Market Areas (DMAs) such as metropolitan areas. For example which radio station in St. Louis has the most listeners between 7 AM and 9 AM, or which newspaper has the greatest circulation in Belleville, Illinois.
SRDS obtains the data from Nielson Ratings.
Here's a sample of the demographic profile data of the St. Louis Region: