Murphy is a city in suburban Collin County, Texas, United States. The 2020 census reported the population as 21,013 compared to 3,099 i…Murphy is a city in suburban Collin County, Texas, United States. The 2020 census reported the population as 21,013 compared to 3,099 in 2000. Murphy is located northeast of Dallas and has a history that goes back to the late 1800s.