Actually, the Colorado Historical Society subscribed to most of the state's newspapers for most of their histories. At one point the issues were microfilmed and the original newspapers were given to local historical societies or museums. The microfilm was later digitized when Colorado became one of the first states in the country to digitize their newspapers (which the Library of Congress was also doing, but at a very slow rate of 10 states per year). That's why Colorado has one of the best online newspaper databases in the country, all free to the user. There are gaps in their subscriptions, so not every newspaper is online. I like to think that it was the foresight of a whole heck of a lot of librarians that led to the wonderful database that exists today, which you can help through donations or by becoming a volunteer subscriber. Unfortunately, for a large city like Denver, very few issues have been digitized, and most of those need to be corrected by volunteers.