The history of Jehovah's Witnesses can be traced back to 1872 when Charles Taze Russell began to lead a Bible study group in Pittsburgh, Pennsylvania. Russell's group was originally known as Bible Students and split into several rival organisations after his death in 1916. One of those groups retained control of Russell's magazine, Zion's Watch Tower and Herald of Christ's Presence, and his legal corporation, the Watch Tower Bible & Tract Society of Pennsylvania and adopted the name Jehovah's witnesses in 1931. Substantial organizational and doctrinal changes occurred between 1917 and the 1950s. The religion's history has consisted of four distinct phases linked with the successive presidencies of Charles Taze Russell, Joseph Rutherford, Nathan Knorr and Frederick Franz.
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