Between 1800 and 1900, women generally married for the first time between the ages of 20 and 22. Less is known about the average age of first marriages for men during the 19th century. In 1890, when the U.S. Census Bureau started collecting marriage data, it was recorded that the average age of a first marriage for men was 26 years, and the average age of marriage for women was 22 years.
Marriage in the Colonies
The average age of a women who married for the first time rose steadily, although not sharply, from 1800 to 1900. North American colonists tended to get married early due to several factors. The first, and perhaps most important, was simply that they could. Many took the advice of the Bible -- to leave home and create your own family -- to heart, and they had the resources to do it. Land was inexpensive, and there was plenty of it to choose from -- it was simple to set up shop. According to a 2010 article in the "Journal of Southern History" titled "The Effect of the Civil War on Southern Marriage Patterns," early colonists married at an average age of around 20 if they were women, and around 26 if they were men.
The Civil War
With the end of the Civil War in 1865 came a "marriage squeeze" for women, especially in the South. About 620,000 men died in the war, which meant that pickings were slim. Many women married older widowers, or married someone not entirely appropriate -- perhaps above or below their socioeconomic status. This pattern did not last very long, however -- about 10 years -- and it did not significantly affect their average age of marriage, which hovered right around 21. For men, it did not significantly change either as many young men rushed to marriage at the start of the war.
After the War
A second rush to marry occurred after the war, but again, the women marrying for the first time were young -- around 21 years of age -- and the men remained right around the age of 26. The age of the women rose slightly because there were more options becoming available to them. A woman no longer had to fully depend on a man to support her -- she could choose to take a wage-paying job. Still, this option was not all that attractive to most women -- marriage and child-rearing were still much preferred.
Age of Consent
During the 19th century, the age of consent in the United States varied between 10 and 16, depending on the state and year. The age of consent was the age when it was determined that a boy or girl -- but most often, a girl -- was capable of consenting to any sexual activity. This does not mean minors often married, however. Although minors could, and still can, marry with parental consent in America, most did not marry so young.