Dame Mary Peters - the 1972 Olympic gold medallist in the pentathlon - pressed the button at the Divis transmitter at around midnight to forever change the UK television landscape.
Prime minister David Cameron said: "The UK's switch to digital television has been the biggest single change to broadcasting for a generation.
"It has delivered more choice for millions of viewers and paved the way for exciting new services, securing our role as a global player in broadcasting and creative industries."
Viewers in Northern Ireland were the last in the UK to transition completely to digital terrestrial TV signals, with many homes enjoying access to Freeview for the first time.
Analogue television started on November 2, 1936, when the first BBC broadcast came from Alexandra Palace in London. But that now makes way for a digital future.
David Scott, the chief executive of switchover body Digital UK, said that today is "a milestone for UK television".
"Over the last five years, switchover has modernised the terrestrial TV network and ensured that the benefits of digital are available to everyone," he said.
"I want to thank the many organisations which played a part in this success and the viewers who generally took the change in their stride. I am delighted we have not only completed the task on time, but also significantly under budget."
The Northern Ireland switch marks the end of the largest capital programme ever in UK TV history, delivered jointly by the BBC and Arqiva, which has dealt with fire, endangered wildlife and disgruntled neighbours to take the UK into the digital age.
As more than 93% of the UK already takes a digital TV service from either Freeview, cable (Virgin Media), satellite via (Sky or Freesat) or IPTV, it is easy to underestimate the significance of the switchover.
But more than 26 million homes have seen their old analogue TV signal turned off in the project, and digital terrestrial signals (Freeview) boosted in their place. More than 10m homes gained access to Freeview for the first time in the switch.
Due to the nature of the UK's TV infrastructure, it was not possible to take the route of the US and other countries involving a single-night switchover right across the nation. Instead, different UK regions had to switch in phases - from the small Scottish islands to the monster Granada TV region serving more than 7.2 million viewers.
The first transmitter switched back in 2009, and along the way Arqiva has faced various challenges as it worked to either upgrade, repair or completely rebuild transmitter stations and their relays to beam hundreds of digital networks.
This included working on the 900-feet high Selkirk mast in perilous weather conditions; and negotiating planning headaches when local residents near the Belmont tower objected to a reduction in height of the mast as they were worried about losing the cache of living near the 'tallest TV transmitter in England'.
Arqiva's work was complicated on the discovery of endangered species near switchover sites, such as grasshopper warblers, wood calamint plants and the Irish hare; and hit by a high profile fire at the Beckley transmitter near Oxford in 2010, rather inconveniently serving the area that was home to David Cameron and communications minister Ed Vaizey.
Since the launch of Freeview in 2002, the UK has seen a big change in TV consumption. According to Ofcom, the average viewer watched four hours of TV per day in 2011, up from three hours, 34 minutes in 2002.
The number of channels broadcasting in the UK in 2002 was 236, but that has risen to 523 in 2012.
Under the switchover project, 10 million viewers have been given access to Freeview for the first time. More than 1,100 transmitters have been re-engineered to boost digital signals, and 1.3m eligible people have been helped to upgrade their TV kit by the BBC-administered Digital Switchover Help Scheme.
Around 70% of UK homes now own an HD-ready TV set. This means that they can access the subscription-free Freeview HD service, which was made possible by the switch to digital signals.
Media regulator Ofcom today welcomed the end of the digital switchover, and said that it paves the way for the next generation of mobile broadband in the UK.
This is because the 800Mhz spectrum previously used for analogue TV is going to be auctioned off to mobile operators so that they can start offering 4G mobile to consumers, capable of delivering speeds up to ten times faster than current 3G on mobile devices.
At the end of 2012, Ofcom will start the auction process and the first 4G services over airwaves previously occupied by analogue television are expected to go live in summer 2013.
Ofcom chief executive Ed Richards said that the digital switchover has been a "huge success".
"Not only has it created more TV choice for consumers, it has also freed up vital capacity that will be used to deliver mobile broadband services to 98% of cities, towns and villages across the UK," Richards said.
"Now that switchover is complete, Ofcom is looking forward to delivering the 4G auction as the next step in delivering new higher speed mobile broadband services."
The UK's major mobile operators have also agreed to set up an independent body called MitCo, which will tackle the expected interference in some Freeview signals from the rollout of 4G over 800Mhz.
Meanwhile, Digital UK is projecting a savings of 37% on its original communications budget of £201m (funded by the BBC licence fee), meaning around £74m will be freed up for other projects.
The BBC-administered Digital Switchover Help Scheme, set up to help vulnerable people convert to digital TV, set out with a budget of £603m. However, it has spent just £260m, meaning that more than £340m will be returned to the government.
The government has already said that some of this freed-up cash will go towards broadband rollout projects in the UK, particularly in rural areas.
Photo gallery - Images from the Crystal Palace TV transmitter station:
Copyright: PA Images