Colo. Rev. Stat. § 3-1-122
Exclusive jurisdiction for all except such as are in sections 3-1-122 to 3-1-124 expressly reserved, over all that tract, piece, or parcel of land known as the cantonment on the Uncompahgre river, in the state of Colorado, known and described as follows: Beginning at the flagstaff on said cantonment, and running thence north sixty-one degrees, four minutes east eighty-six chains, to a point on the eastern boundary; thence north thirty-three degrees west three hundred and twenty-five and thirty-one one-hundredths chains, to the north corner; thence south fifty-seven degrees west and one hundred and seventy-six and sixty-four hundredths chains, to the west corner; thence south thirty-three degrees east four hundred and sixty-nine and fifty hundredths chains to the south corner; thence north fifty-seven degrees east one hundred and seventy-six and sixty-four hundredths chains, to the east corner; thence west one hundred and forty-four and nineteen hundredths chains, to the first mentioned point on the boundary, completing the rectangle, and containing an area of about twelve and ninety-six one-hundredths square miles, or eight thousand two hundred and ninety-three and twenty-five one-hundredths acres. The bearings are true, variation of the needle, December, 1880, fourteen degrees forty-five minutes east; be, and hereby is, ceded, granted, transferred, conferred, and confirmed unto the United States of America, for and during the time the United States shall remain the owner thereof; but, nevertheless, jurisdiction to serve the civil process of state, county, and municipal courts and tribunals, within said tract, and also to serve and execute thereon process in criminal cases by state, county, and municipal officers, in respect of offenses, misdemeanors, crimes, and felonies committed outside of the said tract, is reserved to the state of Colorado.
C.R.S. § 3-1-122