history
Signed September 7, 1901 between Qing China and eleven foreign powers after the Boxer Rebellion. China agreed to a 450-million-tael indemnity (one tael per Chinese person, as a humiliation), execution of officials, and stationing of foreign troops in Beijing. Considered one of the most humiliating of the 不平等条约 (unequal treaties).
memory
辛丑 is the 38th term of the sexagenary cycle, corresponding to 1901. Chinese treaties are commonly named by the year-stem they fell in: 甲午 (1894, Sino-Japanese), 辛丑 (1901, Boxer), etc.