1880 Fed Census for MN, Chisago County, Chisago Lake Township, shows Daniel ARNQUIST married to Anna L. HELIN (!) aged 21, with son Arvid Bernhard ARNQUIST aged 1 yr 6 months.This marriage appears to pre-date that to Anna Lovisa WALLMARK: possible date is 20 Oct 1877.(I previously had this date as his marriage to Anna Lovisa -- it ws provided by word-of-mouth from another researcher.) Also in household in 1880 census was "mother in law" Sarah HELIN, aged 69.
In 1894 a newpaper item listed a niece of Daniel ARNQIUIST, Amanda SWENSON, as being sent to the insane asylum in Fergus Falls, MN. Search of Earl Leaf's Swedes of Chisago County yields just one candidate family: that of Peter August SWENSON, b. 9 Jan 1840 in Herakra parish, Sweden. (This is the only Swenson family with a daughter Amanda in the appropriate area of Chisago County).
If this rings any bells with anyone, I'd be very pleased to hear from you.