It was not. You did have serval deviations from what could be called as "traditional marriage"--such as the Oneida and the Shaker communities. Nevertheless, outsiders and Mormons alike both considered the practic problematic.

In his work entitled Religious Outsiders, Moore discusses that most Mormons were uncomfortable with the practice. Very few actually practiced the principle. Joseph Smith himself kept the Second Vision a secret until he felt safe(r) out on the frontier in Nauvoo. When he unveiled it, along with other controversial doctrines and the destruction of the Expositor which was set to publish a story about polygamy, Smith was assassinated.

The death of Smith led to a crisis in Mormon authority. The prophet left no succession plan. Young took a group west, outside of the US until 1848, where he and branch of Mormonism that came to be called the Latter-day Saints, practiced polygamy until 1890. Some LDS continued to practice the principle. Others became renegades and founded the Fundamentalist branch, but I'm rushing the story.

When the crisis of authority occurred, James Strang claimed that he was the heir to Mormonism in a move fitting to Mormon history. There are doubts if the document he used to claim legitimacy was authentic or not. He moved a group north to Michigan to found the Strangite sect of Mormonism. Originally, Strang denounced the principle, but he then accepted it. The institution of polygamy and other controversial tenets led to his death.

But as for Joseph Smith's son and his widow, they remain in the US. They formed the Reorganized Church of Latter-day Saints in the Midwest. They abhorred the doctrine of polygamy, and denounced. This group of Mormonism was met with very little to no violence.

To say that it was common is a misrememberance of history. It was not even common amongst Mormons.

Edit: I apologize for my typos. I was on my phone at the time.

For Mormons or just in general?