What railroad for which Oakes Ames is credit as being the single most important influence in building was caught up in the  Crédit Mobilier scandal?
Crédit Mobilier of America scandal The Crédit Mobilier scandal of 1867, which came to public attention in 1872, involved the Union Pacific Rail Road and the Crédit Mobilier of America construction company in the building of the eastern portion of the First Transcontinental Railroad. The scandal was in two parts. The construction company charged the railroad far higher rates than usual, and cash and $9 million in discounted stock were given as bribes to 15 powerful Washington politicians, including the Vice-President, the Secretary of the Treasury, four senators, and the Speaker and other members of the House.
IANR Railroad Underpass The IANR Railroad Underpass is a historic structure located in Cedar Rapids, Iowa, United States. It carried railroad tracks for 24 ft over Ely Road. The railroad probably built this stone arch bridge, which was completed in 1887. This kind of structure became more popular in the late 19th century as a railroad bridge because it was more durable than metal truss bridges, and they "projected a refined and sophisticated image." It features a semi-circular arch, a beltcourse, coursed-ashlar masonry, stepped wing walls that are flared, a parapet with projecting coping, and an elongated keystone with the date "1887" carved on it. The bridge was listed on the National Register of Historic Places in 1998. It now carries the Cedar River Recreation Trail over the street.