He was elected to the United States Senate in 1808, and served from March 4, 1809 to March 3, 1815. German was known as a critic of the lack of military preparations made in advance of the War of 1812, and voted against the declaration of war. In 1812 German was one of the founding trustees of Hamilton College. After leaving the Senate, he was judge of Chenango County from 1815 to 1819. He was also a militia officer, eventually becoming a major general.
Supporting DeWitt Clinton's canal project, German also took part in the construction of the Erie Canal after being appointed State Commissioner of Public Works in 1817. German returned to the Assembly in 1819, and served as Speaker. After leaving the Assembly, he resumed the practice of law. German became a Whig when that party was organized.
