On August 30, 2019, he announced that he would not seek re-election for his seat in 2020[1] and was succeeded by fellow Republican Mary Miller.

Shimkus is a lifelong resident of Collinsville, part of the Metro East portion of the St. Louis metropolitan area.

[5] On March 25, 2009, in introductory remarks made to Christopher Monckton, 3rd Viscount Monckton of Brenchley, during a United States House Energy Subcommittee on Energy and Environment hearing, he made the following statement regarding the role of carbon dioxide in global warming: It's plant food ...

[10]Shimkus has quoted the Bible to allay concerns of global warming induced rise in sea levels, stating that God had promised mankind through Noah that the earth would never again be destroyed by a flood.

He has served as one of the chief Republican negotiators on the FDA Food Safety Modernization Act, which was passed by Congress and signed by the president.

Of the bill, he said: "When you're talking about the health and safety of folks, if the FDA has enough evidence to make a declaration of recall, I think that most Americans would support the government having that authority.

[13] Shimkus spoke positively of President Donald Trump's 2017 executive order to temporarily curtail immigration from specified countries until better screening methods are devised.

[16] In 1992, while still serving as Madison County treasurer, he won the Republican nomination to run for the U.S. House seat in what was then the 20th district.

Shimkus announced in September 2005, that he would run for reelection in 2008, despite making a pledge[18] when first elected in 1996 not to stay in office for more than 12 years.

It lost much of its northern portion to the 13th district, previously numbered as 15th, which was ultimately won by his former projects director, Rodney Davis.

When seeking his 11th term in 2016, Shimkus faced Illinois State Senator Kyle McCarter in the Republican primary.

McCarter ran to the political right of Shimkus[19][20] and criticized his accommodation with the Obama administration as well as national Republican party leadership.

FEC records show that the John S. Fund, the PAC for Shimkus, contributed to former Republican House Majority Leader Tom DeLay in 2005.