SISTER GROVE CREEK. Sister Grove Creek rises from the confluence of east and west prongs 2½ miles east of Van Alstyne in extreme southeastern Grayson County (at 33°25' N, 96°31' W). It enters Collin County three miles southeast of Van Alstyne and flows southeast for twenty-six miles to its mouth on Pilot Grove Creek, 3½ miles southeast of Princeton in central Collin County (at 33°09' N, 96°26' W). The surrounding flat to rolling terrain is surfaced by clay loams and deep, fine sandy loams that support water-tolerant hardwood trees, conifers, and grasses. The area historically has served as crop and range land. Tributaries of Sister Grove Creek include Sweetwater, Wolf Run, and Stiff creeks.