Example methods, apparatus and articles of manufacture to estimate local market audiences of media are disclosed herein. Disclosed example methods include determining a first audience metric based on set-top box (STB) return path tuning data obtained from STBs located in a first geographic area. The disclosed example methods also include determining a second audience metric from a portion of audience measurement data corresponding to a different second geographic area, the portion of the audience measurement data associated with monitored sites in the second geographic area having second STB characteristics that correspond with first STB characteristics of the STBs located in the first geographic area. The disclosed example methods further include determining a ratio of the first audience metric to the second audience metric, and processing the audience measurement data based on the ratio to determine an audience exposure metric estimating exposure to media in the first geographic area.