He served in the state legislature, was Surveyor General of the Northwest Territory, was a judge, and was nominated by his party for Governor of Ohio.

The 1802 Ohio Constitution allowed a non-fraudulent debtor to be held in prison until he "delivered up his estate for the benefit of his creditors.

"[5] His efforts in the campaign led to his appointment as Surveyor General of the Northwest Territory, responsible for the states of Ohio, Indiana and Michigan.

[12] After ending his federal service, Johnston became judge of the Superior Court of Cincinnati (1847-1850),[13] which he held until he ran for Governor of Ohio as the Whig nominee in 1850.

"[6] "No person could listen to him and ever forget his clearness of logic, his simplicity, his force of style, his vivid flashes of wit, his mirth provoking humor, his moving elocution.

"[5] He was long associated with Thomas Corwin,[16] including obtaining an acquittal with an argument of self-defense in an 1858 trial when ex-Ohio Governor William Bebb was charged with manslaughter in Illinois.

[5] In 1866, President Andrew Johnson appointed him to the commission to revise the statutes of the United States, where he served for three years.

[5] Johnston married Elizabeth Blackstone of Smithfield Township, Jefferson County, Ohio, and had two sons, who preceded him in death, and two daughters, who survived him.