衛三畏是19世紀最早來華的美國傳教士之一，曾在澳門長期居留。他是第一次鴉片 戰爭前後在澳門生活時間最長的美國人，其間曾協助裨治文印刷英文月刊《中國叢報》，編寫及 印刷其著作《拾級大成》、《英華韻府歷階》，翻譯《聖經》及從事傳教工作等。他寫有大量書 信，除顯示了他的在澳生活外，亦顯示了當時的澳門美國商人／傳教士社區的情況、美國在華政 策及意圖擴張、美中英三國關係等。衛三畏立足澳門，對中國與亞洲有深入的瞭解，他的著作和見識亦使他成為美國漢學的奠基者。

As one of the earliest American missionaries to China, Samuel Wells Williams (1812 —1884) spent nearly nine years in Macau from 1835 to 1844. During his residence in Macau, he wrote quite a number of letters, which are valuable materials for historical study. Those letters not only indicate his life in Macau, but also the situation of American merchants and the missionaries, America’s policies in China and its intention to expand and the triangular relationship of American, China and Britain. Standing on the ground of Macau, Williams gained in-depth understanding of China and Asia. His works and perceptions made him the founder of American sinology.