PEN BRANCH. Pen Branch rises twelve miles south of Guthrie and seven miles east of Haystack Mountain in south central King County (at 33°28' N, 100°20' W) and runs east for fifteen miles through an area of rolling to steep slopes in isolated oil and ranch land before reaching its mouth on North Croton Creek (at 33°25' N, 100°07' W). The locally stony shallow clayey and sandy loams support juniper, cacti, and sparse grasses. Fed by numerous springs, Pen Branch was a large flowing stream in earlier times. In 1854 surveyor Randolph B. Marcy commented that the branch was "clear, deep, and covered with water grasses," and had a considerable salt content. By the early 1970s two small reservoirs, including Parramore Lake, had been built along the creek. Ten years later the branch was mostly dry.