Simplify the following text for a Grade 6 native English-speaking person.
Original: In 1836 , he was elected by the New Hampshire General Court as a Democrat to the United States Senate , serving from March 4 , 1837 , to February 28 , 1842 , when he resigned .
Simplified: In 1836 , he was elected by the New Hampshire General Court as a Democrat to the U.S Senate , serving from March 4 , 1837 , to February 28 , 1842 .