In 1905 his family moved to the Fort Collins, Colorado, area, possibly to alleviate his mother’s asthmatic condition.
In 1912 he opened his own photographic business in Longmont, Colorado, 40 miles southwest of Fort Collins.
In 1914 Miller bought Patrick’s studio in Fort Collins and subsequently moved there, first living upstairs from the studio and then moving to a nearby house.
[2][3] Between 1910 and Miller’s death in 1970 it is estimated he took over 70,000 pictures of Fort Collins landmarks, portraits of local citizens, and local scenery such as the Poudre Canyon near Fort Collins.
The bulk of Mark Miller's photographs were donated after his death to the Fort Collins Local History Archive located at the Fort Collins Museum.