In 1898, Eureka became home to the St. Louis Children's Industrial Farm, established to give children from St. Louis tenement neighborhoods a chance to experience life in a rural setting.

In September 2019, the city's Board of Aldermen voted to annex two commercial lots—one of them a 72.5-acre tract that houses Kirkwood Materials West, a sand and gravel quarry, and the other a 75-acre field, both at highways 109 and FF—located just across the Meramec River in Jefferson County into the city.

[8] The railroad town of Allenton is a former community on U.S. Route 66 located (now) at the junction of Interstate 44 and Business Loop 44 in western St. Louis County.

The town is currently rural, with adjacent farmland and forested Ozark ridges.

[10] This caused the city and U.S. Army Corps of Engineers to evaluate a dozen strategic options, from the use of levees and walls, buyouts of high-risk properties, and the restoration of flood plain as water storage.

[11][12] Scientific researchers determined the flooding was a man-made calamity caused in part by "inaccurate Federal Emergency Management Agency flood frequencies based on the assumption that today's river will behave as it has in the past greatly underestimating our real flood risk and leading to inappropriate development in floodways and floodplains.

"[13][14] The December 2015 North American storm complex deeply impacted the state of Missouri, with heavy rain and snow causing severe floods.

The storm system was responsible for heavy rain that caused severe flooding.

[19][20] A flooding event caused by a strong spring storm system brought multiple rounds of thunderstorms and heavy rain to portions of the Midwest the weekend of April 29–30, 2017.

[21] The middle portion of the Mississippi approached historical record flooding.

The National Weather Service anticipated a 48.5 ft. crest at Cape Girardeau, Missouri, on May 5, 2017, which was within 6 inches of the January 2, 2016 crest of 48.86 ft.[22] The first floor of a church flooded with about 48 inches of water, the same amount as in December 2015.

[23] The 2020 United States census[24] counted 11,646 people, 3,486 households, and 2,575 families in Eureka.

Of all households, 20.1% consisted of individuals, and 11.4% had someone living alone who was 65 years of age or older.

17.2% of all households were made up of individuals, and 5.9% had someone living alone who was 65 years of age or older.

Out of the total population, 3.1% of those under the age of 18 and 5.9% of those 65 and older were living below the poverty line.

[29] Local news coverage for the town and some of its neighbors is provided by the Tri-County Journal, the Eureka and Pacific Current NewsMagazine, and the Washington Missourian.