From ISOGG Wiki
D9S919 is a STR marker located on chromosome 9.
It was previously known as D9S1120 and under this name it was reported that an allele value of 9 was only found in the Americas and far eastern Asia. The presence of an allele value of 9 is therefore a strong indication of native american ancestry somewhere within a person's pedigree.
This marker is available from Family Tree DNA.