This is national chocolate week, and the northwest Iowa-based Palmer Candy Company is having a sweet year. Marty Palmer’s the fifth generation of a family of shopkeepers in what was once a frontier town. Sioux City in 1878 was the jumping-off place for covered wagons heading farther west, and Palmer began as a dry-goods firm, handling merchandise including food. Palmer says chocolate didn’t really become a big item until the advent of refrigeration, and the company had its own ice house. They’d cut it from the rivers in winter, store the ice and use it to haul chocolate, the distance a wagon could go in a day. Palmer says it was a century of success and though the last decade’s been good to the company, it’s not going far from its roots. They make chocolate-covered peanuts and caramels as well as specialty items, but are best known in the Midwest for the signature candy bar, the Twin Bing. Palmer says the Bing candy bar is 80 years old, and a new version includes a caramel center and crispy rice.