In the Old West dream, the Miss Rachel's Place sign had lights flickering on and off. But there are no electrical wires or other apparent sources of electricity to light the sign. Although the battery was around in 1800, it wasn't used as a practicable source of electricity until 1836 when it still wouldn't be a reliable source of electricity for lights bulbs powerful enough to be practical. But then again, one must remember this episode is mostly a dream. And in a dream, anything can happen. And the sign is also part of the joke. So therefore, having a lighted sign for the saloon could be entirely plausible. Moron.