Description from the website of the United States Senate:

"This frequently reproduced cartoon, long a staple of textbooks and studies of Congress, depicts corporate interests–from steel, copper, oil, iron, sugar, tin, and coal to paper bags, envelopes, and salt–as giant money bags looming over the tiny senators at their desks in the Chamber. Joseph Keppler drew the cartoon, which appeared in Puck on January 23, 1889, showing a door to the gallery, the "people’s entrance," bolted and barred. The galleries stand empty while the special interests have floor privileges, operating below the motto: "This is the Senate of the Monopolists by the Monopolists and for the Monopolists!"

Keppler’s cartoon reflected the phenomenal growth of American industry in the 1880s, but also the disturbing trend toward concentration of industry to the point of monopoly, and its undue influence on politics. This popular perception contributed to Congress’s passage of the Sherman Anti-Trust Act in 1890."