The town I grew up in (moved there just in time to start kindergarten and graduated high school from) was Norfolk Nebraska. I'm fairly certain I was the only member of my graduating class to actually consistently say Nor-folk. The vast majority of the roughly 20K population used Nor-fork.

Not surprising, my friends would get rather huffy with me when I'd point out that 'r' is actually an 'l' on the Welcome to sign outside of town.

I came up with two explanations:
1) The good people of Norfolk really had it in for the letter 'l', or
2) The pronunciation was a hold-over from when the town was officially North Fork, as in the North Fork of the Elkhorn River (which is physically where the town is situated).

After decades of careful consideration, I've decided to go with #1.

Brian