Ms Main said the last six years had been the hardest of her life.
"I just hope the new council understands the work this council has done. But I remain sad that we haven't achieved all I'd hope we would."
She said she hadn't always had the full support of council but thanked all the councillors for their input.
"I'm a little bit guilty about leaving but I know I can enjoy myself now."
Presenting Mrs Westwood with flowers and special plaque, Ms Main said her "huge length of service" to the district, first as a county councillor and then with the district council, deserved special recognition
"Nobody will ever know the sacrifices you have made in a local body career closing in on 30 years. And I want to thank your personally for the help and guidance you have been to me," she said.
Mrs Westwood said it had been a pleasure to serve the community.
"The support I've always received from the staff has been very special and I've always appreciated it," she said.
Ms Main said Mr Visser's contribution in just one three-year term had been immense and he had made huge contributions behind the scenes.
"Your decision to stand down is a loss but you make decisions that are best for you. You've been a fine member to have on board."
Mr Visser said it felt "like I'm copping out early" but said he had big challenges ahead with a potential career opportunity in Singapore.
He said Whanganui still faced challenges and while he felt the city had turned a corner there was still work to be done.
"But this place has potential and I know it will succeed."