Is there any way to play Left 4 Dead on a LAN?

It seems the only option for playing Left 4 Dead with my friends is to have all computers online, even though I bought the 4 pack from Valve. Is there anyway to plan a LAN game on Left 4 Dead 1?

It is possible. If you use srcds to set up a dedicated server and note the LAN IP of the computer hosting it, you can enable the developer console in-game (under Keyboard settings then advanced) press the ~ key (on foreign keyboards, it is usually whichever key is next to the 1 key) to open it and enter the command connect <LAN IP of server> into it. You'll then be dropped into the game. Make sure to edit the key of the server so that random people don't start joining. Consider setting it to LAN-only.

If you're using a non-QWERTY keyboard, sometimes binding the developer console may not work. If so, you can edit the launch options and add --console. Then, whenever you launch the game, you'll have console open.