The Cardigan Welsh Corgi is the older of the two corgi breeds, from Cardiganshire in Wales, where it drove cattle by nipping at their heels and stayed low enough to dodge kicks. It's heavier-boned than it looks, with a long back, big rounded ears, a full fox-like tail and colors that include blue merle and brindle. Most weigh 25 to 38 pounds.
Many Cardigans are loyal, steady and a bit reserved with strangers, with a herder's alertness that can show up as barking or heel nipping. In SF, where sidewalks are busy and many homes share walls, early socialization and calm, reward-based training matter. Expect heavy shedding, especially twice a year, and plan on daily walks. Dogs vary, so a Cardigan's own personality matters more than the breed description.