[2] He attained admission to the bar in the summer of 1872 and then undertook a trip to find a location in the Northwestern United States where he could establish a legal practice.

[6] Grigsby also became active in politics as a Republican, and served for two years as clerk of the courts for Minnehaha County, and two terms as a Sioux Falls city alderman.

[3] In the mid-1890s, Grigsby became an advocate of the free silver position with respect to US monetary policy, as well as other reform movements that led to the creation of the People's Party.

[6] As attorney general, Grigsby was responsible for ending the investigation into supposedly missing funds in the office of the State Auditor.

[7] At the start of the Spanish–American War in 1898, Grigsby offered his services to the federal government and volunteered to raise a cavalry unit from South Dakota and nearby states.

[6] Grigsby commanded his regiment as a colonel during May and June 1898, which included its organization and training at Camp Thomas, Georgia.

[8][9] By 1900, Grigsby had returned to the Republican Party, in part because of a longstanding feud with Governor and Populist leader Andrew E.

[10] In May, 1902, President Theodore Roosevelt nominated Grigsby as United States Attorney for the Territory of Alaska’s second judicial district, based in Nome.

[13] Grigsby's tenure was controversial – he had not been recommended for the position by South Dakota's congressional delegation,[11] and he was later reprimanded by the Attorney General for spending part of the winter of 1903 outside Alaska despite explicit instructions not to leave.

[13] In January 1904, Grigsby was accused of accepting a $10,000 bribe disguised as a legal fee in exchange for foregoing prosecution of an Alaska oil company.

[15] Grigsby continued to practice law in Sioux Falls, and remained interested in politics, including attending Theodore Roosevelt's 1905 inauguration.

[19] When conflict between factions in the Mexican Civil War led to the possibility of U.S. military action to defend the U.S.-Mexico border, Grigsby offered to raise a volunteer force and lead it to Texas, but the federal government relied on mobilized National Guard units rather than volunteers to perform this mission.

[21] In 1916, Grigsby was diagnosed with anemia, and he spent time at a sanitorium in Battle Creek, Michigan to receive treatment.

[4] In January 1917, Grigsby announced a new law firm with his son John as his partner,[22] and published accounts indicated he was also active in founding and managing the Stockyards Bank of Sioux Falls.