In 1883, motivated by both his recent diagnosis of tuberculosis and the idea of Manifest Destiny as propounded by Horace Greeley, Pierce moved west.

From 1890 until 1894, he served as Umatilla county clerk, and earned enough money from land transactions to further his education.

He then returned to Illinois with his family to attend Northwestern University, earning his Bachelor of Laws degree in 1896.

After graduation, the Pierce family returned to Oregon, where Walter set up a successful law firm in Pendleton.

From 1896 to 1906, he managed a power company, speculated in land, and became one of the state's most renowned Hereford cattle breeders.

[1] He and fellow owner Parish L. Willis were accused of fraud by another investor, but cleared by the courts of any wrongdoing in 1918.

[2] Pierce won the Democratic nomination for the United States Senate in 1912, but lost to Harry Lane in the general election.

In 1918, Pierce ran, unsuccessfully, as a progressive Democrat against incumbent Governor James Withycombe.

[4] Pierce tacitly accepted the Klan's endorsement and lent his support to the school bill.

He attempted to gain support from progressive Republicans on issues of prison reform, reforestation, and hydroelectric development, but he divided the state Democratic Party by endorsing Robert M. La Follette for President in 1924.

The Ku Klux Klan, which had endorsed him only a few years earlier, began an unsuccessful recall effort.

Pierce and his wife both became involved in the anti-Japanese movement during World War II, in response to a concern on the part of local residents about the success of Japanese truckers in certain areas of Oregon.