National Kentucky Day is observed worldwide every October 19 to recognize Kentucky as the 15th state to join the United States. Established by National Day Calendar in 2017, this holiday celebrates Kentucky's rich history, including its indigenous roots and the impact of European exploration in the 1670s. The state is known as the "Bluegrass State," named after the Kentucky bluegrass that supports its thoroughbred horse industry. Kentucky was formally established as a county within Virginia in 1776 and later became a state on June 1, 1792. The day is part of the National State Days project, which honors states in the order they joined the Union. Observers may engage in activities that reflect on Kentucky's cultural and historical significance, although specific customs are not detailed in the source.