Connect to server using ssh with -L flag?

I got distracted for a while from trying this, and I guess I have my dunce cap on.

I've verified the VNC server is listening, but the LocalForward does not seem to be working.
It's not showing up as an open port when I portscan my localhost address.

theHost has a static IP from my router.
LocalPort is over 1000.

I've got this:

Host theHost
HostName 192.168.1.99
LocalForward localhost:localPort 192.168.1.10:5901

What am I doing wrong? Do I need to restart the Mac? I terminated the SSH connection and reconnected, but with no effect.

Thanks again for your help.