Today's column is about Ray Haysbert, the Parks Sausage executive who died Monday at age 90.

Business "clusters" — a term coined by Harvard Business School's Michael Porter — are local networks of expertise and personalities that create growth beyond what individuals could generate on their own. Haysbert, who died Monday, was a one-man cluster, establishing numerous companies, counseling countless others and serving as a crucial link between Baltimore's earliest black entrepreneurs and today's.

UPDATE: I said Haysbert was 22 when he started with Henry Parks and Parks Sausage, quoting from an old Sun clip. Of course that's impossible, since Haysbert was born in 1920. He would have been closer to 32 when he was hired by Parks. Another reader says, "I wish you had pointed out that Haysbert was a Tuskegee Airman" in Italy World War II. I'm sure he was as proud of that as anything else he did in his life."

I meant to mention it but forgot. And the reader is right. His World War II experience was an important part of who Ray Haysbert was.