Even when she was still the first lady of the United States, Jackie Kennedy had already strong connection with Capri, Italy.  In the mid summer of 1962, in the media heat caused by the mysterious death of Marilyn Monroe on 4 August 1962 and a very open assumption of the actress's liaison with the president, Jackie with her daughter Caroline, accompanied by her sister Lee Radziwill went to Italy. There in Ravello, a small village on the Amalfi Coast, as well as Capri, Jackie was seen with Italian industrialist, future president of Fiat, Gianni Agnelli almost always and his wife Marella Agnelli only occassionaly. So much so that Jackie's husband Jack Kennedy had to send her a telegram: "More Caroline, less Gianni". 

Nobody will ever know if Jackie Kennedy and Gianni Agnelli were romantically linked, but everyone can see she was initiated in la dolce vita de Italy, in a pair of white capri pants, with a pair of Capri sandals custom made for her by the artisan sandal maker Canfora, who also made sandals for Grace Kelly and Princess Margaret. 

After becoming Mrs. Onassis, the wife of the richest man of the world Aristotle  Onassis, Jackie lived in Greece, but Italy, in particular Capri, was her escape, she regularly went there, alone or with her new husband or her two children, or in the company of the jet set like the new Italian designer Valentino Garavani, wearing her white capri pants and custom made Capri sandals in various colors, until the 70s, then everything changed again. Aristotle Onassis died, Jackie Kennedy Onassis went back to New York, her spiritual and final home, living as an intellectual among books.

Capri, as well as Gianni Agnelli, remained but a nostalgia for Jackie, but the way how she wore her capri pants, nonchalantly and elegantly, will remain in our memory.

For the Pre-Inauguration Gala held at National Guard Armory in Washington, D.C. on 19 January 1961, Jackie Kennedy wore a silk floor length gown. It was made of ivory silk satin with a fully lined A-line skirt and elbow length sleeves, and a cockade on right waist, symbolizing her French heritage.  The gown was designed  by fashion designer of Russia Origin Oleg Cassini. who would become her official designer for the next three years.

For the Inauguration ceremony and parade, Jackie Kennedy wore a knee length beige wool coat of three quarter length sleeves, 2 side patch pockets and oversized buttons, which she accessorised with fur muff matching the collar trim of her coat.
Under the coat, Jackie wore a matching beige wool crepe two-piece day dress with round necked crop blouse.

In two days, with just two simple elegant gowns, one coat and one cape, Jackie Kennedy not only became the best dressed first lady up until then, but would become a national fashion icon as well as an international one, for decades to come.

On 12 September 1953, Jacqueline Lee Bouvier married then Senator John Fitzgerald Kennedy at St. Mary's Roman Catholic Church in Newport, Rhode Island.

More than 800 guests witnessed the ceremony. And thousands of onlookers watched it from outside the church.

After their wedding ceremony, the couple spent one night at the Waldorf Astoria before departing for Acapulco, Mexico, where they had their honeymoon.

After the marriage, she would become Jackie Kennedy, and less than 10 years later, she would become the wife of the 35th and the youngest president of USA, the most elegant First Lady in American history, and one of the greatest style icon in the 20th century.

The wedding dress worn by Jackie Kennedy was made of silk taffeta featuring a pleated bodice with portrait neckline, and a pouffant skirt embellished with ruffled florets and intricate scallop pintucks and tiny flowers of wax.

The gown was designed by New York City-based African American designer named Ann Lowe, little known at the time. It took two months to craft, and used 50 kilos of ivory silk taffeta.

Ten days before the wedding, however, the gown was unfortunately destroyed, along with nine other pieces that had been designated and created for the wedding part when Lowe’s Madison Avenue studio flooded, and she had to recreate everything from scratch.

Jackie Kennedy wore an elaborate rose point lace veil with her wedding gown,
and carried a bouquet consisted of gardenias and white and pink orchids.
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Her engagement ring was a 2.88-carat diamond and 2-carat emerald baguette ring set on gold designed by Van Cleef & Arpels.

Side note:

​In the decades after Jackie Kennedy's wedding, her wedding gown has become loved by many brides-to be as well as the general public, she herself, however, did not like it, a wedding gift from her future father-in-law, Joseph Kennedy, father of John Kennedy, and compared it to a lampshade, according to fashion historian Kimberly Chrisman-Campbell, author of the book The Way We Wed: A Global History of Wedding Fashion Kennedy, who thought that Joseph Kennedy wanted to use the wedding and the wedding gown to create an American royalty moment and really set up his son as the heir to the family dynasty.

Ann Lowe, the designer who has created one of the most iconic and photographed wedding gowns of the 20 century, remained little known and died in poverty.

In 2004, half century after Jackie Kennedy's wedding, and 10 years after her death, Marshall Field’s Department Store in Chicago commissioned Belgian artist Isabelle de Borchgrave and her collaborator Rita Brown to create a paper replica of Jacqueline Kennedy’s wedding gown, as seen below, for more information about the creation, please visit JFK library.

Article: The untold story of Ann Lowe, the Black designer behind Jackie Kennedy's wedding dress