De-Industrialization killed many many cities including Baltimore. I know it, you know it and you know I know you know it to be true.
Trying to blame unions is a joke, like you.
I'll post two images that illustrate the decline in urban industrial centers perfectly:
The top image is an old RCA manufacturing plant that was built before 1910 in New Jersey.
The bottom image is the new/expanded Toyota plant in Alabama.
By the 1920s, most of the industrial buildings in the U.S. that were more than 10-15 years old were obsolete. They were not rendered obsolete by outsourcing, or "free trade," or anything of that sort. They became obsolete because the introduction of the assembly line made a massive, single-story building the ideal manufacturing facility -- while the old multi-story model you see in the top image had no purpose in a modern, mass-production business.
Is it even physically possible to fit a building like the Toyota plant in any large U.S. city?
And speaking of auto manufacturing plants, here's a list of a whole bunch of them
that were built in the U.S. after 1980 -- when this country was allegedly seeing a steep decline in manufacturing:
Honda -- Marysville, OH (1982)
Nissan -- Smyrna, TN (1983)
Toyota -- Georgetown, KY (1986)
Mazda -- Flat Rock, MI (1987)
Mitsubishi/Chrysler -- Normal, IL (1988)
BMW -- Greer, SC (1992)
Mercedes-Benz -- Vance, AL (1993)
Honda -- Lincoln, AL (1999)
Nissan -- Canton, MS (2000)
Hyundai -- Montgomery, AL (2002)
Toyota -- San Antonio, TX (2003)
Kia -- West Point, GA (2006)
Toyota -- Blue Springs, MS (2007)
Volkswagen -- Chattanooga, TN (2011)
Notice two things these plants have in common: (1) they are almost all foreign-owned, and (2) they aren't located in old U.S. industrial cities.
There's one foreign-owned plant I left off this list:
Volkswagen -- Westmoreland, PA (1978)
This one was left off the list because it was a complete disaster, and was only open for less than ten years. Volkswagen learned a tough lesson about opening a plant in a state with a dominant labor union presence.