1. The first railroad in the United States to be powered solely by electricity began operating on May 27, 1907 in Philadelphia, Pennsylvania. The line ran from Philadelphia to Bryn Mawr and was a major step in the development of modern electric rail transportation.

2. On May 27, 1952, the U.S. Supreme Court ruled in the case of Pennsylvania v. Nelson that states have the right to require public employees to take oaths of loyalty and to investigate their political affiliations. The decision was controversial at the time and is still debated today.

3. The Pennsylvania Turnpike, one of the first modern toll roads in the United States, officially opened to traffic on May 27, 1940. The turnpike is still in operation today and is considered a model for modern highway construction.

4. In 1964, the musical "Hello, Dolly!" premiered on Broadway. The show, which was based on a play by Thornton Wilder, was written by Jerry Herman and starred Carol Channing. Channing was born in Seattle, but she grew up in San Francisco and began performing in Pennsylvania.

5. On May 27, 1778, the British army under General Sir Henry Clinton evacuated Philadelphia, ending the city's occupation by the British during the American Revolution. The evacuation was an important turning point in the war and helped to secure American independence.