It's not easy to join the President's Club, but once you do, only few can understand the effect it has on you.
That might explain why former presidents have a bond that seems to transcend politics.
From formal events, to galas, fundraisers, and funerals — presidents stay within the same circle and see each other throughout the course of their lives.
In honor of President's Day, we've rounded up the best photos of former US presidents enjoying each other's company.
Former presidents hanging out together
Former presidents hanging out together
COLLEGE STATION, TX - OCTOBER 21: (L-R) Former United States Presidents Jimmy Carter, George H.W. Bush, George W. Bush, Bill Clinton, and Barack Obama address the audience during the 'Deep from the Heart: The One America Appeal Concert' at Reed Arena on the campus of Texas A&M University on October 21, 2017 in College Station, Texas. (Photo by Rick Kern/Getty Images for Ford Motor Company)
JERSEY CITY, NJ - SEPTEMBER 28: Presidents Obama, G.W. Bush, and Bill Clinton smile and wave while on the first tee during the first round of the Presidents Cup at Liberty National Golf Club on September 28, 2017 in Jersey City, New Jersey. (Photo by Shelley Lipton/Icon Sportswire via Getty Images)
Former US President Bill Clinton and former US President George W. Bush speak during the launch of the Presidential Leadership Scholars Program at the Newseum in Washington, DC, September 8, 2014. The program allows individuals an opportunity to study presidential leadership and decision marking and learn from key administration officials, practioners and leading academics. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)
BOSTON - AUGUST 29: Former President Bill Clinton (L) talks with President Barack Obama (R) during funeral services for U.S. Senator Edward Kennedy at the Basilica of Our Lady of Perpetual Help August 29, 2009 in Boston, Massachusetts. Kennedy, youngest sibling to brothers President John F. Kennedy and Robert F. Kennedy, died of brain cancer August 25. (Photo by Brian Snyder-Pool/Getty Images)
LOS ANGELES, CA - NOVEMBER 27: US President-elect Bill Clinton (r) breaks into a big laugh in Los Angeles 27 November 1992, as former U.S. President Ronald Reagan presents him with a jar of red, white and blue jelly beans that, Reagan said, kept him from going to cigarettes. Clinton said he wanted to talk with Reagan about his transition. (Photo credit should read PAUL RICHARDS/AFP/Getty Images)
Five former United States Presidents walk to the opening ceremony of former president Richard Nixon's Library in this file image from July 19, 1990 in Yorba Linda, California. From left to right are, former Presidents George Bush, Ronald Reagan, Jimmy Carter, Gerald Ford, and Richard Nixon. [Reagan, the 40th President of the United States, died June 5, 2004 at the age of 93 after a lengthy illness and will be buried June 11 on his presidential library grounds in Simi Valley, California.]
Rancho Mirage, UNITED STATES: US President George W. Bush (R) bids farewell to former president Gerald Ford (L) and his wife Betty outside of Ford's residence following a courtsey call 23 April 2006 in Rancho Mirage, CA, near Palm Springs. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
354390 98: (File Photo) Ronald Reagan Helps Vice President George Bush Campaign For The Presidency. (Photo By Dirck Halstead/Getty Images)
Before entering Bethesda Naval Hospital for gallbladder surgery, President Lyndon B. Johnson meets with former President Dwight Eisenhower for advice on how to handle the press and public. Wall Street underwent a minor panic during Eisenhower's presidency when he entered the hospital. (Photo by ï¿½ CORBIS/Corbis via Getty Images)
Richard Nixon and Ronald Reagan ride in a golf cart. (Photo by ï¿½ CORBIS/Corbis via Getty Images)
(Original Caption) Los Angeles, Ca. Senator John F. Kennedy and Senator Lyndon Johnson pose after nominations for President and Vice President.
Harry S. Truman (L) and Herbert C. Hoover at Dwight D. Eisenhower's inauguration. (Photo by George Skadding/The LIFE Picture Collection/Getty Images)
UNITED STATES: Unlocated picture of the then US Senator Richard Nixon (1913-1994) (C), Dwight D. Eisenhower (1890-1969) (R) speaking at the back of a car in 1952. Other person on picture is unidentified. Eisenhower supreme commander for the Allied cross-channel invasion in 1944 became president in 1952 with Nixon as vice-president. Nixon was very much involved in the anti-Communist witchhunt instigated by John Parnell Thomas and Senator Joseph McCarthy. (Photo credit should read AFP/AFP/Getty Images)
Former president Harry S. Truman whispers in the ear of President Kennedy at his inaugural ball.
Inauguration of the US President Herbert Hoover (right). With the former American President Calvin Coolidge (left) on the way from the White House to the Capitol. 15th March 1929. Photograph. (Photo by Imagno/Getty Images) *** Local Caption ***