1. On December 18, 1874, George Armstrong Custer and the 7th U.S. Cavalry skirmished with Sioux and Cheyenne warriors at the Battle of Cedar Creek in Montana. This battle was part of the Great Sioux War of 1876-77, which was significant in South Dakota history as it marked the end of Lakota resistance to U.S. expansion and the settling of the Black Hills by white settlers.

2. In 1903, the South Dakota State Normal School (now Northern State University) was established in Aberdeen, South Dakota. This institution played a crucial role in the education and training of educators for South Dakota and beyond.

3. On December 18, 1927, the Rapid City Police Department began using two-way radio communication, making it the first police department in the state to adopt this technology. This innovation helped to improve public safety and was later adopted by police departments across the country.

4. The South Dakota Air National Guard was officially established on December 18, 1946, with the activation of the 175th Fighter Squadron. This unit has played a vital role in defending the United States and South Dakota over the years, including deployments in support of global conflicts.

5. In 2018, South Dakota Governor Dennis Daugaard signed legislation creating an Industrial Hemp Program in the state. This program allows farmers to grow and process industrial hemp for various purposes, including fiber, food, and medicinal products. December 18 marked an important milestone in the state's efforts to diversify its agricultural sector and promote new economic opportunities.