Example methods, apparatus and articles of manufacture to estimate local market audiences of media are disclosed herein. Disclosed example methods include accessing set-top box return path tuning data obtained from a plurality of set-top boxes located in a first geographic area. Disclosed example methods also include determining a ratio of (1) a first audience metric determined from audience measurement data associated with a second geographic area different from the first geographic area to (2) a second audience metric determined from a portion of the audience measurement data identified to be associated with monitored sites in the second geographic area having second set-top box characteristics that correspond with first set-top box characteristics of the set-top boxes located in the first geographic area. Disclosed example methods further include processing the set-top box return path tuning data based on the ratio to determine an audience exposure metric in the first geographic area.