Although Sully has only been with the family for the past seven months following the death of Bush's beloved wife Barbara, the labrador made a huge impact on all he met.
George Bush will receive a state funeral.
Roberto Molina, whose family owns Molina's Cantina, one of Bush's favourite Tex-Mex restaurants in Houston, said he remembers Bush's kindness to his staff whenever he would stop by to eat.
A caption alongside the original Instagram post on Sully's official account read "Mission complete" as the dog prepares to go back to VetDogs to be re-homed with the Walter Reed National Military Medical Centre's Facility Dog Programme which helps other veterans.
Trump declared December 5, as a National Day of Mourning and called on Americans "to assemble on that day in their respective places of worship to pay homage to the memory of President George H.W. Bush".
-The younger Bush asked his dad what he thought about making Dick Cheney his vice presidential choice, and his father approved.
Bush was USA president from 1989 to 1993. The train will take about 2½ hours to travel to the city of College Station, home to Bush's presidential library at Texas A&M University.
Bush - only the second president to see his son follow him to the Oval Office - will be honored with four days of services and tributes in Washington and in Texas, where he will be buried on Thursday.
Trump has said he plans to designate Wednesday as a national day of mourning. While their presence is not yet certain, it's likely that former Presidents Barack Obama, Bill Clinton, and Jimmy Carter will be in attendance as well. He also presided over the end of the Cold War between the United States and the former Soviet Union. A World War II veteran and a CT yankee, Bush moved to Texas after graduating from Yale to pursue a career in the region's booming oil business. The couple was married for 73 years, longer than any other United States presidential couple.
After moving to Texas to work in the oil business, Bush turned his attention to politics in the 1960s. He would go on to serve as ambassador to the United Nations and China, head of the Central Intelligence Agency and chairman of the Republican National Committee before being elected to two terms as Ronald Reagan's vice president.