Hot Country Songs is a chart published weekly by "Billboard" magazine in the United States. 

This 50-position chart lists the most popular country music songs, calculated weekly by collecting airplay data from Nielsen BDS along with digital sales and streaming. 

The current number-one song, as of the chart dated for October 7, 2017, is "Body Like a Back Road" by Sam Hunt. 

"Billboard" began compiling the popularity of country songs with its January 8, 1944 issue. Only the genre's most popular jukebox selections were tabulated, with the chart titled "Most Played Juke Box Folk Records". The chart length was not standardized; a given week had anywhere from two to eight positions. 

For approximately ten years, from 1948 to 1958, "Billboard" used three charts to measure the popularity of a given song. In addition to the jukebox chart, these charts included: 

The names of each chart changed slightly during each chart's life. The "jukebox" chart – which by 1956 was known as "Most Played C&W in Juke Boxes" – ended on June 17, 1957. The "best sellers" and "jockeys" charts continued until October 13, 1958. 

Starting with the October 20, 1958 issue, "Billboard" began combining sales and radio airplay in figuring a song's overall popularity, counting them in one single chart called "Hot C&W Sides". The chart began with a standard length of 30 positions each week. The name of the chart, and the number of positions varied through the years: Its name was switched to "Hot Country Singles" on November 3, 1962; it was expanded to 50 slots on January 11, 1964; then 75 on October 15, 1966; and finally 100 beginning July 14, 1973.
what three charts did they use to measure a songs popularity?
The "jukebox" chart – which by 1956 was known as "Most Played C&W in Juke Boxes" – ended on June 17, 1957. The "best sellers" and "jockeys" charts continued until October 13, 1958. 