Vernonia started to become more than an isolated farming community on July 10, 1924 when the Oregon-American Lumber company opened a state-of-the-art lumber mill, which was supported by a railroad line connecting Vernonia to the rest of the country. Oregon-American merged with Long-Bell in May, 1953, which itself merged with International Paper in November, 1957. International Paper judged the mill antiquated, and closed it on December 20, 1957.
The town was severely impacted by flooding in the December 2007 Pacific Northwest storms, as well as during the Willamette Valley Flood of 1996. At this time FEMA has set up trailers for the displaced residents
Vernonia is located at (45.859846, -123.189125).
According to the United States Census Bureau, the city has a total area of 1.6 square miles (4.1 km²), of which, 1.5 square miles (4.0 km²) of it is land and 0.04 square miles (0.1 km²) of it (2.53%) is water.
There were 789 households out of which 41.4% had children under the age of 18 living with them, 59.4% were married couples living together, 10.4% had a female householder with no husband present, and 26.0% were non-families. 20.9% of all households were made up of individuals and 7.4% had someone living alone who was 65 years of age or older. The average household size was 2.82 and the average family size was 3.29.
In the city the population was spread out with 34.0% under the age of 18, 6.5% from 18 to 24, 30.8% from 25 to 44, 18.9% from 45 to 64, and 9.8% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 99.5 males. For every 100 females age 18 and over, there were 99.3 males.
The median income for a household in the city was $41,181, and the median income for a family was $48,563. Males had a median income of $37,447 versus $24,219 for females. The per capita income for the city was $16,647. About 8.6% of families and 9.7% of the population were below the poverty line, including 12.0% of those under age 18 and 6.4% of those age 65 or over.
Vernonia has been the scene of several films: