[2][3] After graduating from law school, Johnson operated a private legal practice in Winona, Minnesota for five years.

Johnson then lived in Nevada before settling in Ruby City, Idaho.

Johnson established another legal practice with partner William H. Davenport before the two dissolved their partnership.

Johnson worked as a lawyer in Silver City and Ada County, Idaho before relocating to Boise.

Johnson later worked to establish the Boise School District and was the president of the Idaho State Bar.