The baseball cap first emerged in the 1860s, when the members of the Brooklyn Excelsiors donned wide-brim hats to prevent the sun from getting in their eyes. As baseball surged in popularity, fans and other athletes begin to adopt this hat style. Teams emblazoned hats with their logos, and fans collected these caps as keepsakes. In the 1940s, baseball cap designers added latex rubber filling to their caps in order to improve their fit.

Baseball caps are generally made in two styles, short-brimmed and wide-brimmed. Many young people today wear their caps at odd angles or backwards. Basketball, football, field hockey, ice hockey, and golf players all wear 'baseball style' caps. Universities, high schools, even local clubs often design their own caps, which come uniquely emblazoned with logos or ornate pictures.

Truckers and agricultural workers wear special long brimmed baseball caps, commonly referred to as 'trucker hats.' These feature large mesh linings and flat brims. Logos get sewn or printed on the white panel of the front of the cap. In recent years, Hollywood fashionistas have ironically worn trucker hats. Indeed, these hats have been championed by the most luminary movie stars and celebrities, including Lindsay Lohan and Brittany Spears.

Teams regularly redesign their baseball caps, and avid collectors can identify the era and even the production lot of certain caps. Most caps are 'one size fits all,' but large players often have to get their caps resized to fit. In the 1990s, high school kids started a trend of cutting out the inside netting of their baseball caps to create a looser, more casual look.