Came a Mormon also be a wiccan?
No. Being a member of the Church of Jesus Christ of Latter-day Saints (commonly called the 'Mormon' church) means that you believe that the Church is the only completely true religion existing and the only way to salvation. If you are a baptized member of the Church, you are in violation of your baptismal covenants to be an active member in any other religious movement. If you are a Temple Endowed member of the Church, you are in violation of your Temple covenants. You may visit the worship services of other religious groups on occassion, but cannot become a member of these groups.
The Mormon Pioneers moved west on the Mormon trail between 1845 and 1870, when the train came through and became the more common mode of transportation. The biggest years for travel on the Mormon trail were in the 1850's. After the railroad, Mormons continued to move west, but usually came individually as the need for organized companies no longer existed, so the numbers are harder to pinpoint.