The law office now known as Einhaus, Mattison, Carver & Haberman, p.a. and located in the Parrott & Smith Building was founded in 1911 by Harold S. Nelson.  Harold was born in 1890 and practiced at the firm until his death in 1972.  He was a graduate of the Pillsbury Military Academy in Owatonna and was very proud of his military heritage.  He served with the Minnesota Guard on the Texas-Mexican Border, in both World Wars.  Harold attained the rank of Brigadier General in the Army Reserve and is buried at the Fort Snelling National Military Cemetery.  Harold graduated from the University of Minnesota in June, 1911 and ranked number one in his class.  Upon graduation, Harold opened the law office in Owatonna.  A newspaper article described him as "a young man of the soundest principles, ambitious and deeply interested in his profession, and has countless friends in this vicinity."  

Four years later, in 1915, Harold was joined in practice by his father, Soren R. Nelson, who had emigrated from Denmark as a teenager and who became a prominent and successful businessman in Owatonna.  Known locally as S. R. Nelson, he served as Owatonna's mayor from 1912-1914.  Soren had actually wanted his son to enter business with him, but Harold declined to do so, at least until he was established as an attorney.  Not to be outdone, Soren then studied law in his son's office and, in 1915, at age 60, passed the bar exam. Another newspaper article states:  "Twenty candidates took the state bar examination.  Seven passed.  Mr. Nelson, the oldest of the lot, was at the top.  All of the others were university or law college men.  Mr. Nelson was educated in the common schools of Denmark."   (Soren did not attend law school and his formal education was limited to the "common" or non-college prep schools of Denmark.)  Then arose the question of naming the new firm.  Harold wanted to call it "Harold S. Nelson and Father," but Soren had already printed business cards saying "Nelson and Son, Attorneys and Counselors at Law."  That settled the matter and Harold conceded the name to his father. 

In 1921, father and son were joined by Harold's younger brother, Otto J. Nelson.  Otto also served on the Mexican Border and, like Harold, was an Army officer in the First World War.  He graduated from the University of Minnesota in 1921 and joined the firm, which became Nelson and Sons.  In 1931, when Soren died, the firm was known simply as Nelson & Nelson.

In 1946, after serving his country as a pilot in World War II, Byron J. Casey joined the firm as Otto's replacement.  Three years later, in 1949, Wallace M. Tripp joined the practice.  Byron and Wally each pursued lifelong successful careers with the firm until their retirements in 1980 and 1985 respectively.