He represented the old District 20A, which included all or portions of Chippewa, Lac qui Parle, Redwood, Swift and Yellow Medicine counties.

[3] While in the legislature, Frederickson was a member of the Senate Agriculture and Rural Development, Education, Local and Urban Government, Taxes and Tax Laws and Governmental Operations committees, and of various sub-committees relevant to each area.

[3] After Frederickson's service in the legislature concluded, he was elected president of the Minnesota Farmers Union, serving from 1991 to 2002.

In 2002, he was elected president of the National Farmers Union, a national federation of State Farmers Union organizations in the United States and the second largest general farm organization in the country, serving until 2006.

[4] In 2009, he received the NFU’s Meritorious Award for his years of service on behalf of Minnesota and American farmers.