Passing a bar exam at the age of 21, Robertson became one of the most resourceful trial lawyers and legal counselors in the Oklahoma and Indian territories, before statehood.

[1] The fifth child born to a family of six sons and five daughters, Robertson was educated in the Iowa public school system.

While teaching, he was privately studying law and the legal system, and he passed the Iowa bar exam in 1892 at the age of 21.

[4] The job required Robertson to move his family from Chandler to Oklahoma City, where he spent the rest of his years.

[1] Robertson continued to serve as a judge until Governor Charles Haskell, now his friend, chose not to seek re-election in 1910.

Resigning his seat on the court to run for governor, Robertson ultimately withdrew from the Democratic primary to support Lee Cruce.

Robertson tried to get the Democratic nomination for governor, but Robert L. Williams, the popular former Chief Justice of Oklahoma, won it instead.

In 1918, seeking the Democratic gubernatorial nomination for the third consecutive time, Robertson defeated the colorful and popular William H. Murray.

Robertson worked to build on Haskell's policies, leading Oklahoma to overwhelmingly ratify the Eighteenth Amendment, which was added to the United States Constitution on January 16, 1919.

But the state had passed amendments and laws that in practice disenfranchised most blacks by creating barriers to voter registration.

[4] Among Robertson's accomplishments included the passage of various labor laws[8] and the creation of the office of Oklahoma Commissioner of Pensions.

He also established cooperative marketing agencies to serve the state's farmers, who suffered low prices due to agricultural overproduction continuing after World War I had driven up demand.

Robertson's administration struggled with the economic effects of a downturn in the oil industry, and nationwide recession, and the poor economy added to racial tensions in the state.

To help confront this issue, Robertson created a commission on racial relations composed of both white and black members, but it did little to improve things.

In the early morning hours of June 1, 1921, a race riot broke out in Tulsa, where white mobs looted and burned most of Greenwood, the prosperous center of the African-American community in the city.

[9] During the 16 hours of rioting, an estimated 300 people were killed (mostly black Republicans), more than 800 people were admitted to local hospitals with injuries, thousands of blacks were left homeless, as 35 city blocks with 1,256 residences were destroyed by fire, and property damage totaled $1.8 million (nearly $17 million as of 2001 after adjustment for inflation).

[10] Robertson finally regained control in the city by declaring martial law and sending in the Oklahoma National Guard to police the area and end the chaos.

The governor condemned actions by the city and Sheriff's Office and ordered a Grand Jury to investigate,[11] but no one was prosecuted for the deaths, injuries, or damage.

To make matters worse politically, under Robertson's guard the Democrats lost control of the Oklahoma Legislature.

This forced Robertson to operate the government on deficit spending until he called a special session of the legislature to resolve the issue.

He ran for governor again, for Oklahoma Supreme Court justice, and for U.S. senator, but he never held another political office, appointed or elected.