“In fact, men and women often married at a much younger age in the 19th century than we find acceptable today. Historian Kathryn Daynes, who has studied the subject in depth, says that although the female average age at marriage in the United States during the nineteenth century was twenty or older, a girl marrying at age 15 was not uncommon and certainly was not considered abused.”
Some more facts about that...
http://www.freerepublic.com/focus/f-religion/2012278/posts
Even that Mormon link says it was rare. The average age for marriage in the U.S. in 1850 was 22 as shown in the chart in post 35.
Your Mormon page pointed out that marriage laws allowed a girl of ten to marry in England, but it did not mention that in 1850 in England and Wales the average marriage age for single women (first marriage) was 24.71 as the government chart shows in post 38.
From your link:
“For young women, marriage in the early to mid teens was rare, but not unheard of as both the anecdotal and statistical evidence above show.”
That would be BYU Mormon historian Kathryn Daynes. "Her findings include the fact that the percentage of Utah women who married at all was always significantly higher than the national average, the age at which women married was significantly lower than the national norm,"
" Daynes divides her demographic analysis into three periods: 1847 to 1869, Utah's frontier period; 1870 to 1890, years that encompassed the consolidation of settlement and the abandonment of polygamy; and 1890 to 1910, when Mormon marriage patterns moved closer to those of mainstream America. She also classifies the women whose first marriages took place in Utah into three "cohorts," according to the years they were born. Her findings include the fact that the percentage of Utah women who married at all was always significantly higher than the national average, the age at which women married was significantly lower than the national norm, and immigrant women were more likely to enter plural marriages than American-born women. A surprising 36.9 percent of all women's first marriages during the initial period were into polygamy, but this declined to 10.6 percent in the second period. Daynes also found that 24.9 percent of Manti's population lived in polygamous families in 1850, 43.1 percent in 1860, 36 percent in 1870, 25.1 percent in 1880, and 7.1 percent in 1890"
http://www.historycooperative.org/cgi-bin/justtop.cgi?act=justtop&url=http://www.historycooperative.org/journals/ahr/108.4/br_59.html