Mr. Rasmussen spent over 30 years preparing this book. Information was gleaned from newspapers, rare books and special collections at major California libraries. It lists the names of an estimated 15,000 people who crossed the plains by wagon train during the period from April 1849 to October 1852. Some people are listed individually and others as members of groups or companies traveling together. Each listing is preceded by a source citation. About one third of the book is devoted to a surname index, which lists all of the people mentioned in the body of the work. If you feel that your ancestors crossed the plains during this time period, you should definitely check this source for information about them. Also, check for the names of other families that you think might have been traveling with them. NOTE: There was no Volume II completed by the author.