[5] On June 16, 1970, the residents of a trailer court owned by Delbert Johnson voted 49-to-10 to incorporate.

Johnson had started the development in 1959, and in 1968 was unsuccessful in having the area annexed to Gladstone.

The 55th Oregon Legislative Assembly in 1969 established a boundary review board to prevent an increase in small incorporated cities, but proponents of Johnson City's incorporation had filed for an election before the law took effect.

[7] They are also not eligible for North Clackamas Parks and Recreation (NCPRD) programs,[8] which includes Meals on Wheels.

[9] In an effort to join the LINCC, the Johnson City Tenant Collective (JCTC) put Measure 3-585 on the 2022 November General Election ballot.

[10] It did not pass, and there is an open investigation against the owner of Johnson Mobile Estates for possible voter intimidation.

[11] According to the United States Census Bureau, the city has a total area of 0.07 square miles (0.18 km2), all of it land.

40.3% of all households were made up of individuals, and 14.9% had someone living alone who was 65 years of age or older.