Complex sentence: George Anson Pease was a well-known steamboat captain in the Pacific Northwest region on the United States, who was active from the earliest days of steamboat navigation on the Willamette River in the 1850s.
Split into simpler sentences: George Anson Pease was a well-known steamboat captain in the Pacific Northwest region on the United States. Pease became involved from the earliest days of steamboat navigation on the Willamette River in the 1850s.