What is the nickname for the city of Baltimore?

Excerpt from a July 18, 1995 article by Gilbert Sandler in the Baltimore Sun:

"The nickname "Charm City" traces its origins...to 1975...; it grew out of creative conferences among four of the city's leading advertising executives and creative directors...As leaders of the city's largest advertising agencies, they had come together at then Mayor William Donald Schaefer's request to 'come up with something to promote the city. And do it now! I'm worried about this city's poor image.' "

So, short answer: "Charm City" started in the mid-1970s as a promotion by one or more ad agencies.