Brigham Young! He had way more children than Joseph Smith. Thus, Young had more Mormon descendants to further the Mormon movement . Brigham also didn't die as early as Joseph Smith, giving him more time to reign over "Zion"
ANOTHER ANSWER:
As there wouldn't be a Mormon movement without Joseph Smith, I'm going to say that he contributed more... he started the whole thing!
Joseph Smith.
No, the Mormon religion was founded by Joseph Smith and Brigham Young.
Brigham Young colonized many cities as did Joseph Smith.
United States religious leader of the Mormon Church after the assassination of Joseph Smith
Church of Mormon. Brigham Young University (BYU) is a Mormon university.
Brigham Young wasn't really killed, he died of an illness. The President of the Church of Jesus Christ of Latter-day Saints (the "Mormon" church) after Brigham Young was John Taylor.
Brigham Young became a member of the Quorum of the Twelve Apostles of the Church of Jesus Christ of Latter-day Saints (the "Mormon" church) only three years after his conversion from Methodism, in 1835. Because of his position, he was well known among the Mormon community. Upon the death of Joseph Smith, it is said that Brigham Young gave a sermon in which he looked and sounded like Joseph Smith, leading most in attendance to believe that Brigham Young was to be the next leader of the Church. This was in Nauvoo, Illinois.
Brigham Young lead the majority of members of the Church of Jesus Christ of Latter-day Saints (commonly called the "Mormon" church) to Utah after the murder of Joseph Smith.
Members of the Church of Jesus Christ of Latter-day Saints (the "Mormon" church) believe that Joseph Smith's successor was Brigham Young. However, many offshoot groups claim other successors, such as Joseph Smith's son, Joseph Smith III.
Brigham Young had faith.All Mormon's have faith even I do, an 11 year old Mormon.
Brigham Young was the Prophet of the Church of Jesus Christ of the Later Day Saints by the time the Mormon migration reached Utah. Prior to Brigham Young, Joseph Smith, originator of the LDS led the Mormons until he was killed by a mob in Carthage, Illinois, in 1844.The first group of Mormon Pioneers was lead to the Great Salt Lake by Brigham Young. Later groups were lead by experienced trail guides who had traveled with Brigham Young previously.
Brigham Young actually didn't make many changes to the Church. Everything that Brigham Young did was in response to previous instruction given by Joseph Smith. For example, Brigham Young moved the Church to Utah because Joseph Smith prophesied in 1842 that the saints would find peace in the Rocky Mountains. Brigham Young expanded the practice of polygamy, but Joseph Smith had preached in favor of the practice as early as 1831 (polygamy officially began in 1843, still with Joseph Smith's approval). Brigham Young also expanded the practice of consecration (the 'United Order'), which Joseph Smith taught in 1834. (The practice is also found in the Bible and the Book of Mormon.) Brigham Young also expanded temple building (begun by Joseph Smith) and performed temple ordinances, which were given to him by Joseph in 1842.