Bost was raised Baptist and graduated from Murphysboro High School and attended the University of Illinois Certified Firefighter II Academy, later becoming a firefighter. He served in the United States Marine Corps from 1979-82.
Bost ran his family's Murphysboro-based trucking business for ten years. Since 1989, Bost and his wife Tracy have owned and operated White House Beauty Salon in Murphysboro.
Bost was a member of the Jackson County Board from 1984–88, the treasurer of Murphysboro Township from 1989–92, and trustee of Murphysboro Township from 1993–95, until his election to the Illinois House of Representatives.
In 1986, a neighbourhood beagle bit Bost's 4-year-old daughter, who had to get 19 stitches on her face. Animal control officials filed a report stating that she provoked the attack by chasing the dog. Bost, annoyed that there would be a delay in dealing with the incident, retrieved his gun, drove to the owner's home and shot the dog to death while it was penned in an enclosure, which left his neighbours "very alarmed and disturbed." Bost was charged with criminal damage to property and reckless misconduct, but found not guilty.
In 2006, a revolver belonging to Bost was stolen from his gun safe. According to police records, he didn't know about the theft until police informed him that the gun had been used to threaten another man's life. Bost took police to the safe, and found the gun was missing. How the gun was stolen is unknown, but Bost suspects the thief may have been connected to a teenage girl who had stayed briefly in his house. Bost told police that he usually left the room contained the safe unlocked.
Bost was first elected to the Illinois House of Representatives in November 1994, having lost his first campaign in 1992. In his 1994 campaign against incumbent Gerald Hawkins, he was endorsed by the Chicago Tribune.
In May 2012, members of the Illinois House were given just twenty minutes to review and vote on a two-hundred page pension overhaul bill. Displeased with the situation, Bost ranted on the House floor. Bost's rant earned him the runner-up spot on CNN's list of “Best Celebrity Flip-Outs of All-Time". Bost joked about his inclusion on the list, saying "I thought I was going to be No. 1."
In November 2013, Bost presented fellow U.S. Marine Archibald Mosley with Illinois House Resolution 706 for his lifetime accomplishments, including being among the first African-Americans to serve in the U.S. Marines. The presentation was part of a NAACP program.
After the 2014 elections, Bost resigned early from the House so he could take office in Congress. He was succeeded by Terri Bryant.
Bost served on the following state legislative committees:Appropriations-Higher Education
Bost ran for U.S. Congress in Illinois's 12th congressional district. He ran unopposed in the Republican primary, and he faced incumbent Democratic Representative William Enyart in the general election.
Illinois' largely agricultural 12th district leans Democratic, although it is home to many undecided voters, and Enyart was considered vulnerable in the 2014 race. The Cook Political Report rated this race as "Toss Up" and the National Journal believed this district was the 21st most likely to flip Republican in 2014.
In a 2014 radio interview, Bost said some scientists believe in anthropogenic climate change while other scientists do not.
Bost said he ran because "the federal government has basically blown everything they are doing right now." He says he intends to fight for job growth and immigration reform. Bost challenged opponent Enyart to as many as a dozen debates, though Enyart “has thus far replied vaguely to forums.”
Bost was endorsed by the Illinois Chamber of Commerce.
Bost won the election, taking 53% of the vote to Enyart's 42%, with independent candidate Paula Bradshaw taking 6% of the vote.
Bost ran for re-election in 2016. He ran unopposed in the Republican primary election, and faced Democrat C.J. Baricevic and Green Party candidate Paula Bradshaw in the general election. Bost won the general election on November 8, 2016, with 54% of the vote.
Bost was endorsed by the Illinois Education Association, the largest labor union in Illinois. In its endorsement, the union cited Bost's "strong record in support of public education in the Metro East and Southern Illinois."
Bost was sworn into office on January 6, 2015.
In April 2016, a Bost bill to change how the government defines farms and ranches as small businesses passed the U.S. House with bipartisan support.
In February 2017, Bost said that holding town halls with constituents is not "productive," comparing it to the "cleansing that the Orientals used to do where you’d put one person out in front and 900 people yell at them."
On May 4, 2017, Bost voted in favor of the American Health Care Act of 2017.Committee on Agriculture
Subcommittee on Conservation and Forestry
Subcommittee on General Farm Commodities and Risk Management
Committee on Small Business
Subcommittee on Health and Technology
Subcommittee on Investigations, Oversight and Regulations
Committee on Veterans' Affairs
Subcommittee on Disability Assistance and Memorial Affairs
Subcommittee on Economic Opportunity
Bost and his wife Tracy have three children and nine grandchildren.