John Philip Sousa was an American composer and bandmaster who was famous for his marches. For 12 years he was the leader of the United States Marine Band. He then went on to form his own band, with which he toured the world. Although he wrote a few compositions in other genres, including a symphonic poem, they are now forgotten, whereas he was crowned "The March King", so stirring were his compositions in that format.
For many of his marches, Sousa chose 6/8 time. One famous example is Washington Post, another is The Liberty Bell, featured here on Musical Discovery.