While not styled in the traditional model of a congress (with its concave back and dual sheepsfoot blades), the swell center congress pocket knife has a straight main frame with pointed “swells” in the center. The original congress pocket knife arrived on the scene in the early 1800s. Most commonly it is made up of four blades. In modern times, a congress is usually used to describe a knife with 4 blades.
The early market for the knife was the Antebellum South and the blades chosen were those needed to fulfill its agricultural needs (tobacco, etc.). The sheepsfoot blade was used extensively in the cotton and tobacco industry. The coping blade was used for whittling, and the pen blade provided a blade with a point on it. There is a story that U.S. congressmen would be given whittling sticks to pass the time, so they wouldn’t carve into the furniture – maybe this is where the initial description of “a congress knife” came from.
The most famous congress is probably the six blade congress that Abraham Lincoln was carrying when he was assassinated. Today, many people call a 6-blade congress, regardless of the blades configuration a Lincoln congress. The early congress knives, including the Lincoln congress, were made on a slim concave shaped handle.