Complex sentence: In 2001, Tulare became the most productive county in the U.S. in terms of agricultural revenues, at US $3.5 billion annually, surpassing Fresno County's US $3.2 billion, which held the spot for over two decades.
Split into simpler sentences: In 2001, Tulare became the most productive county in the U.S. in terms of agricultural revenues, at US $3.5 billion annually. It surpassed Fresno County's US $3.2 billion, which had held the top spot for over two decades.