1. On June 27, 1945, in Oak Ridge, Tennessee, the world's first controlled nuclear chain reaction was initiated as part of the Manhattan Project. The successful experiment paved the way for the creation of the atomic bomb, which was dropped on Hiroshima and Nagasaki less than two months later, effectively ending World War II.

2. On June 27, 1977, a deadly train derailment occurred in Waverly, Tennessee. Twenty-three people were killed and over 200 were injured in the accident, which was caused by a faulty switch on the track.

3. On June 27, 2015, the Supreme Court of the United States declared same-sex marriage legal in all 50 states, including Tennessee. The ruling was celebrated by LGBTQ+ communities throughout the state and the country.

4. June 27 is recognized as Helen Keller Day in Tennessee, honoring the famous deaf-blind author and activist. Keller was born in Alabama in 1880 but spent much of her life advocating for people with disabilities and championing social justice causes.

5. On June 27, 1919, the city of Chattanooga experienced a devastating flood that killed over 30 people and caused millions of dollars in damage. The flood was caused by several days of heavy rain and resulted in the collapse of several bridges and buildings throughout the city.