Complex sentence: In November 1868, during his fourth term as D.A., Hall was elected Mayor of New York City, and was re-elected in 1870, serving two terms from January 1,1869 to December 31,1872.
Split into simpler sentences: In November 1868, during his fourth term as D.A., Hall was elected Mayor of New York City. He was re-elected mayor in 1870, serving two terms from January 1,1869 to December 31,1872.