A pledge was drawn up in which every signer agreed to purchase a suitable outfit, and to rendezvous at Sapling Grove in what is now the state of Kansas, on the 9th of the following May, armed and equipped to cross the Rocky Mountains to California.
We called ourselves the Western Emigration Society, and as soon as the pledge was drawn every one who agreed to come signed his name to it, and it took like wildfire. In a short time, I think within a month, we had about five hundred names.John Bidwell, The First Emigrant Train to California
After losing his farm in Missouri to a claim-jumper, 20-year-old John Bidwell “resolved to go elsewhere.” He was not the only one dissatisfied with life in fever-ridden Missouri, and after hearing about the benefits and beauty of California from fur trapper Antoine Roubidoux, neighbors and correspondents from as far away as Kentucky and Arkansas signed up to go.
That was in the early months of 1841. Doubts and hesitations soon set in, fueled by the criticisms of local merchants and a newspaper letter that warned of problems with the Mexican government. By May—
membership of the society began dropping off, and so it happened at last that of all the five hundred that signed the pledge I was the only one that got ready; and even I had hard work to do so, for I had barely means to buy a wagon, a gun, and provisions.Indeed, the man who was to go with me, and who was to furnish the horses, backed out, and there I was with my wagon!!
And yet, John Bidwell was determined to leave Missouri and set out for California. He found another partner, gathered a few more people, and arrived at Sapling Grove around May 12. There they found a few more wagons ready to go, and at the last minute, partnered up with a party of Catholic missionaries. By May 18th they were ready to hit the trail.
For more about Sapling Grove as a rendezvous point and the Bidwell-Bartleson Party, you can watch this video from the Oregon-California Trails Association.