Complex sentence: The first known recorded use in Britain was in the Durham coalfield in 1750; however, the use of ponies was never common in the United States, though ponies were used in Appalachian coal fields in the mid 20th century.
Split into simpler sentences: The first known recorded use in Britain was in the Durham coalfield in 1750; however, the use of ponies was never common. In the United States, though, ponies were used in Appalachian coal fields in the mid 20th century.