Why is Dubuque called the "Key City"?

Dubuque, The Key City

Strategically situated on the Upper Mississippi almost midway between St. Louis and St. Paul, Dubuque became known as "the Key City of Iowa." As early as 1858, the Dubuque Express and Herald noted:
"We are at the most important part on the Upper Mississippi, a point which has given our city the sobriquet of "Key City." She commands, as the key, the whole of Northeastern Iowa and Southern Minnesota ... we might go on to show, in addition to her commercial advantages, that Dubuque must necessarily become, in time, a great manufacturing point, from the fact that her advantages for receiving lumber are equal to any other city in the entire West ..."

Within ten years Dubuque's lumber mills were being supplied by rafts of logs from the pineries of Wisconsin and Minnesota. Many other industries also developed, making present-day Dubuque one of the most important manufacturing centers of Iowa.