Answer:
There were 17 origiinal counties created on 1 November 1861. They include:
Arapahoe.
Boulder.
Clear Creek.
Conejos.
Costilla.
Douglas.
El Paso.
Freemont.
Gilpin.
Huerfano.
Jefferson.
Lake.
Larimer.
Park.
Pueblo.
Summt.
Weld.
Twelve earliier counties were established as a part of the creation of the extralegal Territory of Jefferson.
There were no counties in what is now Colorado when it was a part of the Diistrict of Louisiana, the Territory of Miiissouri or the Territory of Nebraska.
Conejos County was originally named Guadalupe County but for only six days.