Complex sentence: The New York Knickerbockers were the first baseball team to use uniforms, taking the field on April 4,1849, in pants made of blue wool, white flannel shirts and straw hats.
Split into simpler sentences: The New York Knickerbockers were the first baseball team to use uniforms, occurring on April 4,1849. Their uniforms were pants made of blue wool, white flannel shirts and straw hats.