For people with Latter Day Saint ancestors, there are many records available to help you with your family tree. In FamilySearch, there are two comprehensive articles (Tracing LDS Ancestors and Tracing Mormon Pioneers) describing records unique to LDS members: https://www.familysearch.org/wiki/en/Tracing_LDS_Ancestors and https://www.familysearch.org/wiki/en/Tracing_Mormon_Pioneers
There are ward and Temple records which can include birth, blessing, baptism, marriage and death dates. There are immigration and migration records of the ships and companies that crossed the plains. Mission records, journals and letters are also available to researchers. You can even request the patriarchal blessings of your ancestors! Three databases will be highlighted in this article.
For those of you with Welsh ancestors, BYU has a Welsh Mormon Immigrant project. Family history students at Brigham Young University are working to document each immigrant through the available records of the time, as well as linking journals, biographies, and photos to each immigrant. Currently, the database contains 5,200 people. If you have any documentation of your Welsh family, donations of photographs, biographies, journals, or other information are welcome. Please contact Ron Dennis at: firstname.lastname@example.org.
The Early Church Information File, 1830-1900 contains more than a million images of index cards in alphabetical order for some early members of the Church. The names on the cards come primarily from sources from 1830 to the mid-1900s. The Early Church Information File (ECIF) was created using various sources including LDS church records, journals, biographies, cemetery records, immigration records and published books. Visit https://www.familysearch.org/search/image/index#uri=https://www.familysearch.org/recapi/sord/collection/2078505/waypoints.
Did you know that the Church took censuses separate from government censuses? The Church took censuses to track members and Church growth throughout the world. The first Churchwide census was taken in 1914. Beginning in 1920, the Church took a census every five years until 1960, except 1945. Information in Church censuses consists of a card with information about each family in a ward or branch. Each person in the household is listed on the family card with their gender, age, priesthood office, and marital status.
Each time the census was taken, additional information was included, especially in 1920 when they added the maiden name of married women, year of birth of each person, and the Church auxiliaries each person attended. Then in 1925 the complete birth date is included. The 1930 census adds the exact place of birth. Cards for Kentucky, North Carolina, Tennessee, Virginia, West Virginia, and parts of Maryland also provide exact baptism information. Visit https://www.familysearch.org/wiki/en/LDS_Census.