The pearl button industry employed thousands of mussel fishermen known as clammers. With minimal start-up cost, the button industry’s demand for shell, and the potential to find valuable pearls, clamming became the Mississippi Rivers gold rush. As mussel beds became depleted, clammers moved to rivers throughout the Midwest.

Clammers and their families set up riverbank camps where several families sometimes formed a village of tents and crude buildings. Men worked the shell beds while women and children steamed the mussels open, separated mussel shells, set up camp, and prepared meals.

From his boat the clammer could employ a number of shell collecting methods. The most common method involved the crowfoot bar, consisting of a bar, hooks, line, and rope. The crowfoot played to the mussels instinct to snap shut when an object entered its opening.

As early as 1908, and continuing into the 1920s, the clamming industry averaged between 40,000 and 60,000 tons of shell annually at a value of $800,000 to over $1,000,000.

Clammers first worked the waters nearest to Muscatine and eventually spread into nineteen states as the industry grew and local mussel beds were depleted. The first warning signs of mussel bed depletion came within a decade of the industrys start. In 1908 Congress established the Fairport Biological Station, located outside of Muscatine, to study mussel propagation. The button manufacturers helped support Fairports research. Nearly 300 different species of freshwater mussels are native to North America, and 75 species are native to the Midwest. About 10 percent of North American mussels are extinct. Another 210 species are at risk of disappearing. While the pearl button industry commonly used about a dozen species, environmental factors further threatened the mussels existence. Pollution, silting, and dredging destroyed the mussels habitat.