The smallest tectonic plate is the Juan de Fuca Plate. It is located off the northwestern coast of the United States and Canada, primarily under the Pacific Ocean. The size of the Juan de Fuca Plate is about 250 kilometers (approximately 155 miles) wide and extends for about 1,200 kilometers (around 750 miles) in length.
This plate is a remnant of the larger Farallon Plate, which has mostly been subducted beneath the North American Plate. The Juan de Fuca Plate plays a significant role in the tectonic activity of the region, particularly in contributing to the seismic activity along the Cascadia Subduction Zone, where it is slowly sliding beneath the North American Plate.