Complex sentence: Only in 1816, after the Supreme Court had existed for a quarter-century, did Congress created an official post of reporter and added a $1,000 a year salary in the Judiciary Act of 1817.
Split into simpler sentences: Only in 1816, after the Supreme Court had existed for a quarter-century, did Congress created an official post of reporter. It then added a $1,000 a year salary in the Judiciary Act of 1817.