The Pomo became comparatively wealthy among the Californian tribes by making small cylindrical beads from clamshells. When strung, these beads served as a standard of currency throughout the region. The Pomo counted strung beads into the tens of thousands, as documented through the names given to the numbers and a few ethnographic observations. No trace of the ancient Pomo number system is found archaeologically, illustrating a key challenge in investigating prehistoric number systems. The practice of counting beads was related to, and presumably motivated by, the value the beads achieved from the amount of labor it took to produce them, along with their widespread use as standard currency. The practice of counting beads, along with the need to count them in significant quantities, meant the Pomo number system expanded to very high numbers. The names of the Pomo numbers were directly related to the way the beads were strung and then bundled for the purpose of counting them. The Yuki, one of the Pomo’s near neighbors, had a number system based on the number eight, along with a unique decimal-octal counting sequence presumably used with beads.