Many wore the red, white and blue of the US flag or caps with Trump’s Make America Great Again slogan.
“I look at him as a Christ martyr, definitely,” Monica Mireles, a 44-year-old Texan who drove 12 hours to get here, said of Kirk.
Kirk, 31, was shot in the neck on September 10 while speaking at a Utah university as part of his popular public debate series.
Authorities arrested a suspect after a 33-hour manhunt and prosecutors said they will seek the death penalty.
The killing of the founder of Turning Point USA, a right-wing youth action campaign, has inflamed acrimonious and violent political divisions in the United States.
Authorities say the suspected 22-year-old gunman cited the “hatred” he believed was stoked by Kirk – who was a vitriolic critic of transgender people, Muslims and others.
Kirk used his millions of social media followers, the massive audience of his podcast and appearances at universities to bolster Trump with young voters and fight for a nationalist, Christian-centric political ideology.
Even before the alleged killer was identified or arrested, Trump called Kirk “a martyr for truth and freedom” and blamed the rhetoric of the “radical left.”
The US president has lauded Kirk’s role in helping him get re-elected in November last year.
Crackdown on liberal ‘terrorism’
Trump, Vice President J.D. Vance, Secretary of State Marco Rubio and Defence Secretary Pete Hegseth will all speak at the memorial.
Also speaking will be Director of National Intelligence Tulsi Gabbard, Health Secretary Robert F. Kennedy jnr, conservative commentator Tucker Carlson and other prominent Trump administration officials.
Kirk’s widow, Erika Kirk, who is taking over the reins of Turning Point USA, will also address the audience at the State Farm Stadium in Glendale.
In response to the killing, the White House last week declared it would crack down on what it terms “domestic terrorism” by the political left.
Trump said he would designate “Antifa” – a shorthand term for “anti-fascist” used to describe diffuse far-left groups – as “a major terrorist organisation,” a move he threatened in his first term.
Prominent late-night talk show host Jimmy Kimmel was yanked off the air Wednesday, hours after the government threatened to cancel broadcasting licenses because of comments he made about Kirk’s killing.
The moves have sparked alarm among Trump’s critics who warn of possible steps to silence dissent of his divisive right-wing White House tenure, marked by a rolling back of social justice policies and an immigration crackdown that has seen widespread complaints of rights abuses.
