Born in Coatesville, Pennsylvania in 1885, Isabel Branson entered the Philadelphia School of Design for Women in 1902, where her teachers were Elliott Daingerfield and Henry B. Snell. The school's "Alumnae Award," which Cartwright won in 1906, allowed her to study abroad for one year. She chose to work under the dynamic figure painter Frank Brangwyn in London, but traveled through Holland, France, and Italy. In addition, she was one of Snell's students in Bruges.

The painter married John Reagan Cartwright in November of 1911; the couple moved to Terrell, Texas, where Isabel lived until her husband's death in 1917. Cartwright later had one-woman shows in San Antonio and Fort Worth, Texas. One critic noted how ...