There were quantitative reasons for this date of origin. Tsar Alexander II was assassinated by a bomb on March 13, 1881, and ushered in a wave of official and popular antisemitic violence known as pogroms in which individuals were killed, cultural institutions sacked, and property destroyed. The reaction raged at its most extreme in the years 1881 and 1882, during which there were scores of violent events throughout the southern and western regions of the Russian empire in which Jews were permitted to dwell. A wave of emigration followed, with the number of Jewish immigrants to the United States rocketing from less than 35,000 for the entire decade of the 1870s to more than 175,000 during the decade of the 1880s.