I'm looking for information about my great-grandfather, Per Jonson (this is the spelling used in the United States, maybe the same in Sweden).

I have very little information about Per Jonson-(as given here):

Per Jonson was born December 10, 1830 in Sweden. He married Elna Andersdotter who was born October 10, 1844 in Sweden in the Krams forsamling, Kristianstad's Lan where she spent her youth. They were married in 1856 in Sweden and came to the U. S. in 1881. They had five children that I know of who went by the following names in the Svea, Minnesota, area: John Per (J. P.) Johnson, Andrew Per (A. P. Johnson), Pete Per (P. P.) Johnson, Hannah Johnson, Emil (Per?) Johnson. I'm fairly sure the first four children were born in Sweden. Andrew Per Johnson was born on February 26, 1872 in Vestra Vram, Skone, Sweden. He received his U. S. citizenship in Kandiyohi County, Minnesota, on December 9, 1896. On his Declaration of Intention and Clerk's Certificate, it says that he emigrated to the United States and landed at the port of New York on or about the month of June in the year 1881 (at least Per, Elna, John, Andrew, Pete and Hannah). Andrew was my grandfather.

Elna had a sister (Karna Andersdotter--also known as Carrie) who married Mons Swenson. They came to the United States from Sweden. I was told the following: Karna and Mons were both from south Skåne, Sweden. Karna (used Anderson as her maiden name in the U. S.) and Mons Swenson married when she was either 18 or 19 years old in Sweden. They bought land in Sodra Rorum, Skåne, Sweden, and stayed there until 1868 when they came to the United States on a steamer.

Mons was born August 4, 1832 in Horby, Malmohus Lan, Sweden.
His father: Sven Mattison, born 1796, died April 10, 1843
His mother: Bengta Bengtsdotter

Karna was born August 24, 1842 (Number 2 Ostentorp, Skane, Sweden). I'm not sure whether that is Sodra Rorum or not. They were married in 1861. When they came to the United States, they had four children with them: Elna (born 1862), Elsie (born May 7, 1864), Swan M. (born October 10, 1866 at Number 2 Gunarp, Ostentop), and Andrew (born June 24, 1869). There were more children born in the Svea, Minnesota, U. S., area. All of these children used the surname of Swenson, at least in the U. S. I do not know whether all of these four children were born in the same place, but it is likely. A later child, Hilda C., was born and was my grandmother. She and Andrew P. Johnson were first cousins and married so both of these families are my relatives.

A second cousin told me that Karna's parents were as follows:

Father: Anders Akesson, born September 5, 1802 (O Wram)
Mother: Hanna Pehrsdotter, born March 29, 1821 (Esphult)
They were married November 3, 1839

Hanna Pehrsdotter's father: Perh Perhrsson, born Brentorp, Esphult, Linnergot
Hanna's mother: Else Tykesdotter, born 1793 (Djuorrod)

Elna had another sister who married Anders Jonson (I do not know if he is related to Per). I have almost no information on them. I suspect they married in Sweden and later came to the United States. I do know they had three children: August A. Johnson, Martin A. Johnson, Betsy. I do not know whether the children were born in Sweden, but that is likely. I do not know Mrs. Anders Jonson's first name.

Karna had a brother (known as John Anderson in the U. S.). I have no other information about him.

An obituary from about 1920 in the U. S. stated that there was a brother in Sweden and a sister in Denmark. A second cousin of mine said that (from looking at Swedish history) this Denmark might not be the actual country known today as Denmark.