January Jones was born on January 5, 1978, in Sioux Falls, South Dakota. She is named after January Wayne, a character in Jacqueline Susann’s potboiler novel turned film, Once Is Not Enough. She is the daughter of Karen Cox, a store manager; and Marvin Jones, a gym teacher and fitness director. She is of Czech, Danish, English, Welsh, and German descent. She has two sisters, Jacey and Jina.
Her family moved to Hecla, South Dakota, (population 400) in 1979, but they moved back to Sioux Falls in 1996. She graduated from Roosevelt High School there.