In 1932, Morrison graduated from Louisiana State University in Baton Rouge. He completed his law degree from LSU as well in 1934. After graduation, he moved to New Orleans, where he became an attorney with the National Recovery Administration, a New Deal agency. Thereafter, he was a law partner with both Jacob Morrison and the future Democratic U.S. Representative Thomas Hale Boggs, Sr. He was a second cousin of Marie Corinne Morrison Claiborne Boggs, who succeeded her husband Hale Boggs in Congress in 1973.
As an active Democrat, Morrison in 1939 helped to organize the People's League of Independent Voters in New Orleans. In 1940, Morrison was elected to the Louisiana House of Representatives for the 12th Ward; he became a reliable floor leader for the reform faction led by Governor Sam Houston Jones. One of his colleagues was his future ally and rival on occasions, William J. "Bill" Dodd, from Allen Parish.
During World War II, Morrison left the legislature to join the United States Army. He rose to the rank of colonel, and became chief of staff of the occupation forces stationed in the city of Bremen. In 1942, he married Corinne Waterman of New Orleans. He received the Bronze Star and also served in England, France, and Belgium. He was reelected to the legislature in absentia in 1944, as was Bill Dodd in Allen Parish.
A proponent of increased international trade, Morrison lent his support to the construction of the International Trade Mart - precursor to the city's World Trade Center - and traveled extensively in Latin America to promote trade with New Orleans. He became friends with dictators Rafael Trujillo and Juan Perón. Another remnant of Morrison’s attempts to increase ties to Latin America is the statue of Simón Bolívar that still stands at the corner of Canal and Basin streets.
Despite running on a platform stressing the elimination of the Old Regular machine, after his election Morrison quickly built his own political organization, the Crescent City Democratic Association. Modelling itself on the Old Regular system of ward and precinct captains, the CCDA began finding its supporters jobs in City Hall and in municipal construction contracts. His organization's power quickly eclipsed that of the Old Regulars, and he secured easy re-elections in 1950, 1954, and 1958.
In 1954, Morrison traveled to Shreveport for the inauguration of newly-elected Mayor James Creswell Gardner, I, who served a single four-year term. Gardner undertook similar reforms in Shreveport of the kind that Morrison had triggered in New Orleans. The two became good friends over the years.
Throughout most of the 1950s, scandals continued to emerge concerning the involvement of the NOPD in graft and vice. Not only was the NOPD accused of refusing to stop prostitution and gambling, but there was evidence of NOPD involvement in protection rackets for vice operations. In 1952, the Metropolitan Crime Commission was established as an independent monitor of the NOPD and the Morrison administration’s approach to vice. State Police Colonel Francis Grevemberg, later a two-time gubernatorial candidate, led a series of high-profile raids on New Orleans gambling establishments that embarrassed Morrison and the NOPD for its inactivity. Eventually, Aaron Kohn was sent from Chicago to investigate NOPD involvement in vice; he soon complained that Morrison was obstructing his efforts. Morrison refused to fire Joseph Schuering, the NOPD superintendent implicated in the scandals, until sustained political pressure forced the mayor to ask for Schuering’s resignation in 1955.
New Orleans gained national notoriety during the fall of 1960 as the city’s school board implemented a federal integration order for its public schools. A handful of black students entered two white schools in the city’s Ninth Ward, but were greeted with mobs of white women and youths screaming racial slurs and throwing bottles and refuse. While Morrison did not join Governor James Houston "Jimmie" Davis' drive to prevent integration by shutting the schools down, he also did nothing to prevent the segregationist demonstrations. The NOPD stood by and allowed the mobs to continue, while at the same time, police arrested civil rights activists holding lunch counter sit-ins in the city. Morrison’s lack of action stemmed from his political need to avoid alienating black supporters while at the same time retaining a segregationist stance. His position resulted in criticism from both sides; black New Orleanians and supporters of civil rights felt he had betrayed them, while hard-line segregationists accused him of supporting integration.
Morrison had a longstanding ambition to become governor of Louisiana, and he ran unsuccessfully for that office three times.
In the election of 1956, Morrison lost to Earl Long. The ascerbic Long ridiculed Morrison as a "city slicker" out of touch with residents of small towns and in rural areas. Long laughed at his opponent's unusual first name deLesseps (pronounced DEL ES SEPPS: "Ole De la Soups is the only man that can talk out of both sides of his mouth, whistle, and strut all at once."
In the election of 1959-60, Morrison lost to former Governor Jimmie Davis, a singer of both popular songs and gospel hymns. He polled 414,110 votes (45.5 percent) in the runoff to Davis' 487,681 (54.1 percent). Davis was endorsed in the runoff by the third-place candidate, segregationist William Monroe Rainach of Claiborne Parish. Morrison was endorsed by the fifth place candidate, Bill Dodd, but Dodd's showing had been insufficient to help Morrison that much.
In the primary runoff, Morrison's lieutenant governor choice, then Alexandria Mayor W. George Bowdon, Jr., lost his race to Clarence C. "Taddy" Aycock of Franklin in St. Mary Parish, a former Speaker of the Louisiana House.
In the election of 1963-64, he lost to Public Service Commissioner John Julian McKeithen. Each time, he was strongly opposed in the northern half of the state because of his perceived liberal views, particularly on race (though he was a declared segregationist), and his Catholicism. In the 1964 primary, Morrison ran with the Houma (Terrebonne Parish) attorney Claude B. Duval, who sought the office of lieutenant governor. Duval, a longtime personal friend of Morrison's, was defeated by his St. Mary Parish neighbor, incumbent Clarence C. "Taddy" Aycock, who ran as an independent that year, meaning that though he was a Democrat, he was not allied with a gubernatorial candidate.
His reputation was further tarnished in the aftermath of the school integration crisis, and his political future was uncertain. He was the first of many New Orleans mayors to attempt to amend his 1954 city charter to allow a third consecutive term as mayor, but the failure of this effort left him without a certain political future.
Seeking a political base from which to stage another run for governor, he approached the John F. Kennedy administration and was appointed Ambassador to the Organization of American States on July 17, 1961. In a further sign of his declining political fortunes, his chosen candidate for mayor in the New Orleans election of 1962 – State Senator Adrian G. Duplantier – lost the Democratic runoff to Victor Schiro.
Morrison ran for governor for a third time in 1963-64, but was defeated by John Julian McKeithen of Columbia in tiny Caldwell Parish in the runoff. Only four months after his final election defeat, Morrison was killed in a plane crash in Mexico.
Morrison married Corrine on October 3, 1942. Mrs. Morrison (born August 17, 1921) died at the age of thirty-seven on February 26, 1959, just a few months before her husband launched his second gubernatorial bid.
His older son, deLesseps Story "Toni" Morrison, Jr., who like his father had been a state representative, ran unsuccessfully for mayor in the 1977 New Orleans mayoral election. "Toni" Morrison died of lung cancer on August 21, 1996. Both Chep and Toni Morrison died at the age of fifty-two. All four Morrisons are buried in Metairie Cemetery in New Orleans.
The Morrisons had a daughter too, Corinne Ann Morrison (born 1947), a New Orleans attorney.
"The Morrison funeral was a moving and impressive event. A motorcade formed in front of the Capitol House Hotel [in Baton Rouge] at 8:45 a.m. on Tuesday, May 26, 1964. There were about twenty automobiles led by the governor [John McKeithen]. I rode down with four other state representatives in Representative Spencer Todd's brand new Cadillac. Others in the car were Conway LeBleu, Joe Henry Cooper, and Steve Dupuis. It turned out that Steve lived next door to my cousin . . . in Opelousas.
"When we arrived in New Orleans we went to the new City Hall and were joined by Mayor Victor Schiro and thence to Gallier Hall, where the bodies [Morrison and son] were in state. Gallier Hall is an architecturally magnificent old building that had been the City Hall for most of Chep's tenure. It was there that I had attended one of his staff meetings in 1955.
"The public viewing was now completed and our visit was special. The body was in the former waiting room for the mayor's office. . . At the door were smartly uniformed firemen and policemen. The room itself was still adorned with large fine paintings . . . The two-star flag of a major general with black streamers hung over the flag-draped coffin which was attended by a military honor guard. Chep loved things military and would have approved of the arrangements.
"We were officially greeted by Jimmy Fitzmorris (later lieutenant governor) who was chairman of the New Orleans City Council. Jimmy, also a friend of mine, had been asked by the Morrison family to handle all of the arrangements which he did in splendid fashion. Everything seemed so right. I found it easy to visualize the excitement of the room when Chep ruled from there."
". . . The mass lasted about an hour. . . . A military presence was still evident as all of the pallbearers were Army officers. . . . Life was going on as a great and good friend departed it."