In America, people from Sze Yup generally worked as laborers; Sam Yup people worked as entrepreneurs; and Chung Shan people specialized in agriculture. The Punti-Hakka Clan Wars also erupted in the Sze Yup counties just prior to this time period of emigration. In 1851, two wuiguns (native place associations) were established in San Francisco: the "Sze Yup Wui Gun" and the "Sam Yup Wui Gun". Endowed with only limited arable lands, with much of the terrain either rocky or swampy, Sze Yup was the "pre-eminent sending area" of overseas Chinese.