Complex sentence: In February 1817, when John Tayler became Acting Governor of New York after the resignation of Daniel D. Tompkins, Swift was elected President pro tempore of the State Senate and was Acting Lieutenant Governor of New York until July 1,1817.
Split into simpler sentences: In February 1817, when John Tayler became Acting Governor of New York after the resignation of Daniel D. Tompkins, Swift was elected President pro tempore of the State Senate. He was Acting Lieutenant Governor of New York until July 1,1817.