Like many of the more “interesting” elements of Mormon history, I had never heard about the Kinderhook plates growing up. The basic premise is that some men “found” (made) some metal plates and Joseph Smith translating a portion of them. Obviously the question arises, how could Joseph Smith translate something that was later found to be a forgery?
Here are some quotes about them:
“I have seen 6 brass plates… covered with ancient characters of language containing from 30 to 40 on each side of the plates. Prest J. has translated a portion and says they contain the history of the person with whom they were found and he was a descendant of Ham through the loins of Pharaoh king of Egypt, and that he received his kingdom from the ruler of heaven and earth.” (William Clayton’s Journal, May 1, 1843, as cited in Trials of Discipleship – The Story of William Clayton, a Mormon, p. 117)
“I insert fac-similes of the six brass plates found near Kinderhook, in Pike County, Illinois, on April 23, by Mr. Robert Wiley and other, while excavating a large mound. They found a skeleton about six feet from the surface of the earth, which must have stood nine feet high. The plates were found on the breast of the skeleton and were covered on both sides with ancient characters. I have translated a portion of them, and find they contain the history of the person with whom they were found. He was a descendant of Ham, through the loins of Pharaoh, king of Egypt, and that he received his kingdom from the Ruler of heaven and earth (History of the Church, vol. 5, p. 372)
“Church historians continued to insist on the authenticity of the Kinderhook plates until 1980 when an examination conducted by the Chicago Historical Society, possessor of one plate, proved it was a nineteenth-century creation.” (Rough Stone Rolling, Richard Bushman, p 490.)
You can check out these sites for more information:
fairmormon.org (apologist site)
mormonthink.com