This book reveals how Congress quietly shaped American elections across more than a century of constitutional development. Far from a passive observer, Congress used its authority to influence key controversies – from the expansion of slavery in new territories to the reconstruction of the post-Civil War electorate. Congress exercised power under the Elections Clause, the Guarantee Clause, and later, the Fourteenth and Fifteenth Amendments, to combat voter suppression, reimagine representation, and determine who could (and could not) participate in American democracy. Even as Jim Crow laws disenfranchised millions, Congress continued to review and sometimes overturn the elections of its own members, refusing to cede complete control to the states. In doing so, Congress routinely subordinated federalism to politics. In Congress We Trust? provides a new perspective on who truly governs our system of elections by showing that federal authority has been broad, lasting, and decisive.