Complex sentence: In the mid 1800s, sheep that were most likely of the Merino, Rambouillet (French Merino), or Churro breed were brought to Santa Cruz Island, by the 1860s thousands of sheep grazed freely on the island.
Split into simpler sentences: In the mid- 1800s, sheep that were most likely of the Merino, Rambouillet (French Merino), or Churro breed were brought to Santa Cruz Island. By the 1860s thousands of sheep grazed freely on the island.