When first lady Pat Nixon stepped off Air Force One in Beijing nearly five decades ago, little did she know that her tea-length red wool coat would become a symbol of the new friendship between China and the US.

This summer, that coat is among the nearly two dozen favorite fashion items of first ladies on display at the Why They Wore It: The Politics and Pop Culture of First Ladies' Fashion exhibition, which runs from Aug 1 to Sept 12 at the Nixon Library and Museum in Yorba Linda, California.

The exhibit features authentic and replica dresses of first ladies that are made to appear they are on a fashion runway.

First lady Melania Trump's Dolce & Gabbana gown, which she wore during the 2017 G7 Summit, is also being displayed for the first time during the exhibit.

But the coat that Mrs. Nixon wore while accompanying her husband Richard Nixon during their historic trip to China in 1972 is being shown for the first time in six years.

Xie Yuan, vice-president of the Chinese People's Association for Friendship with Foreign Countries, who was invited as a guest speaker to the exhibition's opening ceremony, said Mrs. Nixon played a pivotal role as a friendship ambassador between the two countries during the Nixons' celebrated visit.

"Chinese people were especially impressed by the red coat that she wore during that visit. That red coat was so special and dazzling among all the gray, blue, brown and dark clothes worn by the Chinese people at the time. It conveys a natural feeling of warmness and friendship," he said.

President Nixon was the first US president to visit China. His trip ended 25 years of non-communication between China and the US and led to the opening of diplomatic ties between the two countries.

Pat Nixon's coat has since appeared in numerous historical photographs in which she posed with Chinese citizens.

"Her warm smile and elegance, together with those famous photos taken during that trip, will stay forever in Chinese people's memories and in the history of China-US relations," Xie said.

Carl Sferrazza Anthony, guest curator of the exhibit and an expert on first ladies, said it's hard to know now why Mrs. Nixon decided to wear the red coat.

"It may seem obvious to us now, and we can only speculate that she intended it to be an extension of good luck, that it was intended to speak to the ancient Chinese culture and the ancient meaning and symbolism of the color red," he said.

The color red, which symbolizes good luck in China, also represented Mrs. Nixon's well wishes for a budding friendship between the US and China, Anthony said.