When
Illinois was admitted as a State into the Union, McLean was elected to the
Fifteenth Congress and served from December 3, 1818, to March 3, 1819. He failed to be re-elected in 1818 to the
Sixteenth Congress. He was also an unsuccessful candidate for congress in the 1820 and 1822 elections. He was elected to the
Illinois State House of Representatives in 1820, 1826, and 1828, and served as speaker. In 1824, McLean was elected to the
United States Senate to fill the vacancy created by the resignation of
Ninian Edwards and served from November 23, 1824 to March 3, 1825. He was unsuccessful in a bid for re-election, not managing to get more than 12 votes of the 27 needed in the legislature through 10 ballots, but resumed the practice of law. He was again elected to the
United States Senate and served from March 4, 1829, until his death, aged 39, in
Shawneetown, Illinois in 1830. He was interred in Westwood Cemetery, near Shawneetown. ==Legacy==