The rally brought together nearly 3000 supporters of the party from across the country.
Leaders and representatives of other parties in the country were also in attendance.
These included National Reconciliation Party leader Hamat Bah and a representative of the GPDP, while PDOIS sent a written statement, which was read on their behalf.
Speaking at the rally, UDP Secretary General Lawyer Ousainou Darboe said that in 1996 several Gambians who believed their country should have democracy came together and formed the UDP.
The party had faced a lot of adversities from outside forces, while some people have been tortured and some lost their lives in the fight for democratic values, over the years, he added.
The UDP secretary general recalled the day 27 September 1996, and said that was the day UDP’s election victory was “stolen” by the then PIEC – Provisional Independent Electoral Commission.
Today, the UDP wants to ensure the IEC is independent, Darboe said.
The UDP’s 18th anniversary is worth celebrating, according to the UDP leader, who said his party did pioneer a campaign to lift the ban on opposition parties in The Gambia.
The Gambia’s opposition parties have suffered more than blacks in Apartheid South Africa, Lawyer Darboe went on.
When the APRC appointed their propaganda secretaries as chiefs, it was the UDP which challenged it, he continued.
Lawyer Darboe denounced the back way to Europe, and was quick to add that it is both a national and international problem that should be discussed. “We should also discuss youth employment,” he further stated.
“If there is any seriousness in this government, the money they are misusing can be used as a revolving fund to train youths on skills,” the UDP leader said.
Former minority leader and MP for Kiang West, Momodou Lamin Sanneh, also speaking at the rally commented on the importance of the 18th anniversary of the party.
He said the UDP has gone through difficult times in The Gambia, but this did not make people to give up.
“Those who defected have now regretted it,” he said, adding that Darboe has been talking to The Gambia for 18 years now, but has never lied to the Gambian people.
Sanneh said they do not hate the ruling APRC, “but hate its rules and policies.”
He also said all Gambian resident in the sub-region should have chance to vote, like citizens of other West African countries who live here.
“And we should have a term limit in this country, instead of an age limit,” he added.
Hamat N.K. Bah, party leader of the NRP, in his solidarity statement delivered on the occasion said, “18 years is small for the life of a party, but 18 years as an opposition party in Gambian politics is hell.”
He also said when the UDP was formed in 1996, different interest groups came together and the party secretary general lawyer Darboe was able to manage them.
Hamat Bah highlighted a lot of troubles and tribulations lawyer Darboe, and other staunch UDP party members and their families, had to go through to see UDP alive and kicking today.
“Some people lost their jobs, some lost their properties during the commission of enquires, some later defected,” Hamat Bah recounted.
At the time Darboe took up the UDP’s struggle, he was among the four leading lawyers (in the country). “He lost some of his properties because of UDP and Gambia,” the NRP leader told the large gathering of keen listeners.
“Ousainou’s family is facing all sorts of harassment,” Mr Bah went on. “It is difficult to lead a party, because you must be ready to face all necessary sacrifices, but the struggle is just starting,” he declared.
Aja Amie Secka, the national secretary of the UDP women’s wing, said at the time of establishing their party “it was very hot because at that time human rights and democracy was not there.”
UDP was established in difficult times, she asserted, adding that some of their members died during the struggle to lead the party to where it is today.
“UDP will take charge in 2016,” Ms Secka declared.
Other speakers at the mass rally, chaired by Lamin Dibba, former MP for Central Baddibou constituency, were Kemeseng Jammeh and Dembo Bai Force Bojang, former MP for Bakau.
