Answer
The Crédit Mobilier scandal involved members of Congress in 1872-73, in which they were bribed by the Crédit Mobilier of America, a railroad construction company, to approve land grants and loans for the Union Pacific Railroad. Colfax, the Speaker of the House of Representatives, was one of the most prominent members of Congress implicated in the scandal. The scandal led to Colfax's resignation from Congress in 1873.