WASHINGTON—President Donald Trump is set to open the “Great American State Fair” on Wednesday night in Washington, marking the beginning of the 16-day celebration of the nation’s 250th year. The president is expected to deliver remarks at 8:30 p.m. ET in a rally-style event. On June 4, Trump announced on Truth Social that he would hold what he described as “the Greatest Rally, EVER” in Washington to mark America’s 250th birthday. He said the event would feature speeches, patriotic music, military bands, and performances by country music singer Lee Greenwood and classical crossover artist Christopher Macchio. The fair will be the first national exposition of its kind, inspired by the World’s Fairs. It runs from June 25 to July 10 on the National Mall, celebrating America’s rich history....