To that end, Union Pacific purchased a bankrupt lending institution in 1864 and renamed it after a well-known and prestigious French firm, Crédit Mobilier. The new holding/construction company accepted stock and bonds from Union Pacific at face value, but sold them to investors at rates under par. To make up for the loss, Credit Mobilier overcharged for constructing the railroad. Since the Union Pacific’s board of directors ran Credit Mobilier, they were able to make an estimated $16.5 million in profits, and by the time of the railroad’s completion in 1869 the value of Union Pacific stock had risen 750%.

Congressman Oakes Ames of Massachusetts was a member of the House Pacific Railroad Committee, and had financial interest in an Iowa railroad which he wanted linked to the transcontinental railroad. Ames assigned his contract to Credit Mobilier, and in 1867 and 1868 sold the company’s stock to other congressmen at par value, far below its market price. There were no down payments and the stock remained in Ames’s name, with recipients given a document certifying their shares. In a letter, Ames divulged that he distributed the stock shares "where they will do the most good to us."

Rumors soon circulated of the clandestine deals, but no action was taken until the fall of 1872 when a disgruntled Credit Mobilier stockholder allowed the New York Sun to print a series of incriminating letters from Ames. They appeared too late to have any impact on the presidential or congressional elections, but when Congress reconvened, an official House investigation was headed by Congressman Luke Poland of Vermont. An expulsion resolution against Ames failed, but he was formally censured for his part in the scandal. Several other elected officials were implicated, but not punished. Most argued that they had merely accepted a gift, not a bribe.

In this cartoon, the politicians, "disgraced in the eye of the public for owning Credit Mobilier stock" stand in front of the Capitol (left). The group on the far-left includes (left-right): a seated Vice President Henry Wilson (Republican, Massachusetts); Senator James Harlan (Republican, Iowa); former vice president Senator Schuyler Colfax (Republican, Indiana); and, Senator James Patterson (Republican, New Hampshire). The group farther to the right includes (left to right): in the center with arms linked and holding Credit Mobilier ("C. M.") dossiers are a bespectacled Congressman James Brooks (Democrat, of New York) and Congressman Oakes Ames (Republican, Massachusetts), whose file is marked "Bait"; in the shadow behind Ames is Congressman (and future president) James Garfield (Republican, Ohio); Congressman John Bingham (Republican, Ohio); a bald Congressman Glenni Scofield (Republican, Pennsylvania); in front, a bewhiskered Senator Henry Dawes (Republican, Massachusetts); and, on the far right is a sulking Congressman William Kelley (Republican, Pennsylvania).

Yet, the cartoonist’s ire seems to be aimed primarily at the press, to which an angry Justice paraphrases the New Testament: "Let him that has not betrayed the trust of the People, and is without stain, cast the first stone." As a firm supporter of President Ulysses S. Grant and his Republican administration, Nast was often at odds with many other journalists, and the recent presidential election in 1872 had been a particularly bruising affair.