The Trump administration changed US trade policy toward China in ways that will take years for researchers to sort out. This paper makes four specific contributions to that research agenda. First, it carefully marks the timing, definitions, and scale of the products subject to the tariff changes affecting US-China trade from January 20, 2017 through January 20, 2021. One result was that each country increased its average duty on imports from the other to rates of roughly 20 percent, with the new tariffs and counter-tariffs covering more than 50 percent of bilateral trade.