The first European explorers to visit the area, Father Marquette and Louis Jolliet, arrived in 1673,[3] where they encountered the fearsome painting of the Piasa bird.

The Romanesque Revival style courthouse is a magnificent architectural structure of limestone quarried from the nearby town of Grafton, Illinois.

Today, while the county maintains its agricultural base, it is also within commuting distance of jobs and industry in St. Louis, Missouri and the surrounding area.

The bordering rivers play an important part in Jersey County's economy by supporting agricultural producers and agribusiness, and by creating a strong tourist market.

Spring is the wettest season and produces severe weather ranging from tornadoes to snow or ice storms.

Fall is mild with lower humidity and can produce intermittent bouts of heavy rainfall with the first snow flurries usually forming in late November.

In recent years, average temperatures in Jerseyville have ranged from a low of 17 °F (−8 °C) in January to a high of 88 °F (31 °C) in July.

[citation needed] It voted solidly Democratic until Warren G. Harding carried the county in his record 1920 landslide.

It voted Republican again in Herbert Hoover's landslide of 1928, but otherwise was firmly Democratic until World War II, when opposition to US involvement turned the county to Wendell Willkie and then Thomas E. Dewey.

Disagreement with the Democratic Party's liberal views on social issues since the 1990s has caused a powerful swing back to the Republicans in the past quarter-century.

[18] As is typical of the Upland South, Hillary Clinton in 2016 did far worse than any previous Democrat, while Joe Biden performed marginally better in the 2020 election.