Founded in 1836, Union Theological Seminary sought to be a school where moderate theological views could be taught in the heart of America’s most important city, New York City. Scholars have recognized Union’s role in the fundamentalist-modernist controversy of the 1920s, but few have noticed its impact in Chinese Protestantism. From 1911-1949, 196 Union alumni - an average of five students for each graduating class - went to China. Thirty-nine of these former students were Chinese nationals. Many of these Chinese graduates became key leaders in China’s Young Men’s Christian Association, the Christian colleges in Republican China and the Three-Self Patriotic Movement. Men such as Y.T. Wu (Wu Yaozong), K.H. Ting (Ding Guangxun), Timothy Tingfang Lew (Liu Tingfang), William Hung (Hung Ye), and Andrew Y.Y. Tsu (Zhu Yuyue) provide interesting case studies into how Union influenced Chinese Christianity. I apply insight from two sociologists, James Davison Hunter and Mark Granovetter, to new archival findings to contend that Union Seminary developed a dense network of influential Chinese and American Christians in the Sino-Foreign Protestant Establishment. The New York seminary acted as a social hub where Christian leaders established and strengthened their relational ties. Over time these ties formed a dense social network that influenced Sino-American relations and Chinese Protestantism. Union advanced the indigenization of Christianity in twentieth century China, helping “Christianity in China” become “Chinese Christianity. Union's role in China has been largely unnoticed until now.