For those doing industry research, particularly looking a the past, looking at marriage and marital status information may be of interest.
One of the first stops may be the Statistical Abstract of the United States (linked below). According to introductory information in the "Vital Statistics" section of the Statistical Abstract for 2006, data on marriages and divorces have been collected at the national level since 1887-88. Periodic updates took place after 1888, with annual updates beginning in 1944. Data for earlier years can be found in earlier editions of the Statistical Abstract.
Statistics on the total number and rates of marriages in the United States at the national and state levels is compiled by the National Center for Health Statistics (NCHS) in the National Vital Statistics Reports, formerly the Monthly Vital Statistics Report (MVSR). One of the earliest comprehensive analysis was issued by NCHS in 1995 and appeared in the Advance Report of Final Marriage Statistics, 1989-90. [PDF: 201 KB/ 24 p.] However, those numbers have since been updated in "First Marriages in the United States: Data From the 2006–2010 National Survey of Family Growth" [PDF: 420 KB/ 22p.] published in 2012.
Additional data on marriage in the United States can be found in The National Survey of Family Growth (NSFG). Conducted by NCHS, the data was published in Series 23, Number 22, "Cohabitation, Marriage, Divorce and Remarriage in the United States" [PDF: 5.5 MB/ 103 p.] The Vital & Health Statistics Series 24 "Compilations of Data on Natality, Mortality, Marriage, and Divorce" contains several reports.
Statistics can be found in the reports collection in another section of this guides as well as