The French term "presqu'île", the origin of the park's name, means "peninsula", or, literally, "almost an island". Despite the name, Presque Isle has been an island for brief periods of time after it has been cut off from the mainland several times since 1819—the longest stretch was from 1832 to 1864. In the 1950s, in an effort to combat erosion, the state and federal governments built sets of concrete seawalls and perpendicular groins. In 1992, a series of 58 breakwaters were also constructed to help capture sand and significantly slowed its movement eastward. Even with the substantial engineering projects, sand has to be relocated from tombolos that form behind the breakwaters, and new sand has to be brought in annually to replenish the beaches.