Steiwer was a conservative Republican who represented three rural Eastern Oregon counties in the state senate.

Throughout his adult life, Steiwer operated a 35,000-acre (14,000 ha) sheep and cattle ranch in Wheeler County, Oregon.

He continued to work at the Steiwer and Carpenter Bank and became involved with community organizations, joining the American Legion and the local Elks lodge.

[14] During the Great Depression, he began helping farmers and ranchers secure the loans they needed to stay in business.

In 1931, United States Secretary of Agriculture, Arthur M. Hyde, appointed Steiwer to the Oregon Drought Relief Committee.

The committee was responsible for organizing an agricultural credit corporation in Oregon to facilitate the farm loan process.

[15] In late 1934, James P. Yates, the District 18 state senator who represented Gilliam, Sherman, and Wheeler counties resigned halfway through his four-year term.

[18] In the general election, held two weeks after the nominations were filed, Steiwer won the District 18 seat, allowing him to finish the final two years of Yates' four-year term.

Steiwer represented District 18 at the special session which began on October 21 and finished its business and adjourned on November 9.

[26] As a result, Steiwer was unopposed in the general election and retained his senate seat representing Gilliam, Sherman, and Wheeler counties.

He also served on assessment and taxation, banking, insurance, military affairs, public lands, resolutions, and roads and highways committees.

[28][29] Since state senators served four-year terms, Steiwer did not have to run for re-election prior to the 1939 legislative session.

He was also a member of the livestock, forestry and forest products, irrigation and drainage, resolutions, and revision of law committees.

[34][35] After the session was adjourned, the senate president appointed Steiwer to an interim study committee on industrial development.

The committee was directed to review tax laws and other incentive that might help encourage new businesses to locate in Oregon.

[40] At the close of the session, Steiwer made appointments to a number of interim committees that were tasked to study specific topic and present their finding to the next legislature.

While serving as acting governor, he appointed a new district attorney for Wheeler County as well as performing other state duties.

[49] A long-time member of the Oregon Wool Growers Association, Steiwer was elected president of that organization in 1949.

In 1951, he traveled to Washington, D.C. to testify before the United States Congress on behalf of the wool grower association.

In his testimony, Steiwer voiced the association's opposition to wool and lamb price controls and related subsidies.

[53] In 1955, he was appointed to a two-year term on the board of directors of the Portland Branch of Federal Reserve Bank of San Francisco.

[54] Also, Steiwer had planted a large tree farm on his Wheeler County ranch property in the early 1950s.

president of the Northwest Livestock Production Credit Association, a director of the Keep Oregon Green Association, and a director of the Columbia Basin Electric Cooperative, which provides electric power to users in Gilliam, Morrow, Sherman, Umatilla, and Wheeler counties.