Birth, Marriage and DeathVital records for Boone County can be found online and at libraries, so before making a trip to the courthouse, check out the records that are already available online and on microfilm.
Boone County birth records are currently being indexed on FamilySearch.org and many are available now. The State Historical Society of Iowa's reading room has birth records from 1880-1904 and 1906-1932 available on microfilm. The Iowa Genealogical Society library has county birth records on microfilm from 1880-1932. Both of these libraries are located in Des Moines, Iowa.
Boone County Births from 1904 - 1906 can be found here. Thank you NettieMae for the transcriptions.
Boone County marriage records from 1850-1900 are available on this site. Marriage records from 1850-1934 are currently being indexed on FamilySearch.org and many are available now. The original records can also be viewed on microfilm at the State Historical Society of Iowa (1861-1928) or the Iowa Genealogical Society (1851-1902).
Some death records can be found on this site. These records are also being indexed on FamilySearch.org. Death records on microfilm are available at the State Historical Society of Iowa (1880-1921) and the Iowa Genealogical Society (1880-1934).
The State Historical Society of Iowa also has naturalization, probate, divorce, deed/land records and more available on microfilm. Check its website for where resources can be found. Once on this page, scroll down then enter the county.