There'd be no The Wire without The Corner and an honorable mention to Homicide: Life On The Street

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It's somewhat of an unofficial loosely connected prequel to The Wire in certain aspects. If I'm not mistaken, it was more popular and acclaimed than The Wire was during its initial run.
The Corner is a bit more gloomy, gritty, dreary, and rather depressing due to the subject matter, there's not a lot of “fun/light-hearted” moments you see on The Wire.
I remember seeing this when I was a kid during reruns, early 00s, usually with my parents, and I had no clue a show such as The Wire even existed since being a kid, shows like that don't even catch your attention 'cause you're busy watching cartoons and Disney Channel.