What was important about the Bidwell party?
"Prior to the year 1841, only a few emigrants had made the westward journey overland to Oregon and California. The formation of the Western Emigration Society in 1841, however, permanently changed this situation. Organized in western Missouri to help overland emigrants prepare for the journey westward, the Western Emigration Society influenced the large migration that followed in the 1840s.
John Bidwell had migrated to western Missouri from New York in search of adventure, and his ambitions coincided with the aims of the Western Emigration Society. After a meeting with mountain man Antoine Robidoux, who painted an attractive picture of California, Bidwell was determined to head westward to California. The party that he traveled with was the first planned overland company to emigrate to California.
Bidwell's diary was carried to the eastern states and published in 1842. It was read and carried by westward travelers, becoming the first overland emigrant "guide." The diary of James John was not discovered until the twentieth century, and was published first in 1991 in Doyce Nunis's book The Bidwell-Bartleson Party: 1841 California Emigrant Adventure, along with the Bidwell diary and other documents relating to the emigrant party. The two diaries complement each other. "
Source and more details:http://scienceviews.com/bidwell/bidwellbackground.html