The club first came into existence in 1873 as Trinity Recreationists and joined the Second Division of the Football League in 1896. However, they were denied re-election after finishing bottom in 1902 and saw a host of attempts to re-enter the Football League rebuffed.
From then on, league restructuring has been the only reason for the club changing divisions, with neither a promotion nor relegation to speak of.
However, that all came to an end at the weekend as they surrendered a two-goal lead against fellow strugglers Telford, conceding three goals in 15 minutes to lose 3-2 and drop into the Northern Premier League.
The defeat left them in 20th place in the National League North on 43 points from 41 games and confirmed their relegation.
Trinity have won 13, drawn four and lost 24 of their 41 games this season after avoiding the drop by just one point last year.
Speaking to 'BBC Radio Lincolnshire' following the Telford game, chairman Richard Kane expressed his disappointment with the relegation, but insisted that manager Lee Sinnott would be retained.
"We've not been relegated in 145 years, but nor have we been promoted either," he explained.
"Hopefully, we can go straight back up next season and break another record.
"And Lee Sinnott is definitely in the plans for next season. He's very experienced, he's not paid a fortune and we've seen a difference since he came in. He's not paid a fortune and he likes the club."
Kane believes that Gainsborough's status as a part-time club was part of the reason behind their demise, with even the sixth tier of English football now full of fallen giants and full-time outfits.
"We have to be honest, for the past two or three seasons we've been knocking on the door," he said.
"We could not have done anything else with our limited resources. This is now just a big money league and it's difficult to compete.
"There's 10 teams in there that are full-time, with a playing budget in excess of £20,000 a week.
"We're a small market town with a population of less than 20,000, playing teams like York, which has a population of 200,000.
"We live and die by what we've got. Other teams are out there spending more than they bring in, but that's football."