Johanes(John) Wedemeier/Wedemeyer 25 Feb 1826

I am trying to locate my ancestors. The furthest back I have been able to go is Johanes Wedemeier (my great great grandfather). He went by the name John. I have his death certificate but no parent information is listed. He was born in Hanover, Saxony, Germany on 25 Feb 1826 and died in St. Louis, Missouri on 3 Apr 1912. He married Franciscka ? and they had 7 children. Came to the United States sometime before 1859 when there oldest child was born. There children are Elizabeth 1859, Anton 1863, John 27 Jan 1866(which is my Great Grandfather), Clementina 1870, Francis 1872, Joseph John 18 Nov 1875, and Theresia 1878. Any help with this would be greatly appreciated. I am completely stuck here. Thank you.