What we know
The first Castle Rock PO (April 5, 1871); in 1872 'a little store and a water tank as yet monopolize the corner lots' (News); Douglas PO 1874-1886; platted July 28, 1880 by the National Land & Improvement Co.; stone quarries (rhyolite).
Where it was
Center of Sec. 22, T8S R67W, from Place Names of Colorado ('Rural Post Office 1874-1886. Previously Castle Rock'), via the BLM PLSS survey grid; good to about half a mile. Crofutt (1881) and Hall (1891) both put Douglas 'three miles south of Castle Rock' on East Plum Creek and the D&RG; the section center is 2.2 miles south of downtown Castle Rock.
Placed from a written description, such as a land section, a distance from a landmark or an old survey note.
Sources
Sources are named in the text above. Numbers such as S-0080 refer to our source list. Most newspaper quotations were read in the Colorado Historic Newspapers Collection. Long quotations from recent books are shortened here.