Located in an interesting building on Rice, this is a rather dated and dusty collection of Kauaiiaana - if you are after interactive displays stay away. However, if you are prepared to read, there is some interesting material on the sugar plantations which really helped us to understand some of what we had seen driving round the island. Upstairs there is also a good section on the experience of Japanese Americans on Kauai in WW2 which is not as sanitized as some of the museum displays on Oahu. Also told here is the full story of the Japanese pilot who crashed on Niihau after the Pearl Harbor attack and what happened to him, right down to the tail light from the plane.
Surprisingly good museum shop for a small museum. Worth a stop, preferably after doing the island by car.