NDP MP Olivia Chow was joined by hundreds of people in Toronto — along with others in similar events across the country — to celebrate the life of her husband Jack Layton, one year after he died from cancer.

"Today is a sad day but it is also a good day a day to remember Jack’s life, a day to remind ourselves of the values he taught us, a day to renew our commitment to continue his work," Chow told the crowd assembled in Nathan Phillips Square.

The memorial event is being called a "celebration of love, hope and optimism," a reference to a portion of Layton's last letter which was to be read during the ceremony.

• PHOTO: Jack Layton tribute fence panorama

It will also feature performances from Ron Sexsmith, Raffi, Jason Collett and Lorraine Segato. Organizers have also promised other surprise guests.

Layton would have "loved" the display, Chow said, but would then have insisted people "stop mourning and go make a difference."

"Go party tonight, but work together to create a better Toronto, a better country, because it is possible," she said.

Chow was joined on stage by Layton's children, Mike and Sarah.

"This past year, hearing from all of the Torontonians and Canadians from across the country about how my dad’s vision of a Canada where we have a more loving, hopeful and optimistic society has meant so very much to all of us," Mike Layton, a Toronto city councillor, said, "and has helped our family cope throughout this difficult time."

Admirers scrawl chalk messages

Before the event, Layton's ashes were interred at the Toronto Necropolis cemetery, one of the city's most historic burial sites.

"There is a real sense of finality that Jack’s ashes have been buried," Chow told CBC's Power & Politics host Evan Solomon before the start of the memorial event. "It was quite difficult, but it was a very beautiful moment also because we were surrounded by his loved ones, his family, his friends."

Layton died on Aug. 22, 2011, at the age of 61, less than four months after leading his party to opposition status in the general election, a surprising feat and a first in the NDP's 50-year history.

In the days that followed, mourners in Toronto took to where he first made his political mark as a Toronto councillor outside city hall at Nathan Phillips Square — and covered it with tribute messages using chalk.

Toronto street artist Dave Johnston has been commissioned by the NDP to colour the pavement at the square for Wednesday's memorial event, just as those thousands had done a year ago.

"I always brushed politicians with the same brush," said Johnston. "But his speech at the end, that's what inspired me about the guy."

A number of admirers returned to the same spot Wednesday to scrawl their own messages of optimism, including Kenn Bell who wrote the words "the future is bright."

"I think it's definitely an extension of [last year's tribute], just the idea that Jack is a lasting individual, not only a great smile, a great moustache, but a great individual who's done a lot for federal and municipal politics," he said.

Mike Layton said earlier Wednesday that people continue to share their thoughts on how his father changed the city almost every day.

"I was over on Toronto islands recently, and someone sitting on their front porch ran over to me and said, 'This is the house that Jack saved,'" said Layton.

Events planned in other cities

While the Toronto gathering is the marquee event to mark the first anniversary of Layton's death, other events were organized across the country, including in St. John's, Quebec City, Sudbury, Winnipeg, Regina and Vancouver.

Organizers in Calgary planned to serve Orange Crush and stream the Toronto event online.

The NDP's sweep of Quebec in the last federal election that pushed Layton into the role of Official Opposition leader was known as the Orange Crush because it's the NDP's trademark colour.

In Ottawa, people gathered at the Centennial Flame on Parliament Hill Wednesday morning for a vigil and planned to hold a picnic in a park later in the evening.

NDP MP Paul Dewar spoke to a number of Layton admirers in Ottawa where he listed a number of his party's priorities, including restoring full health-care coverage for refugees.

Later, Dewar was unapologetic about the partisan messaging at the memorial.

"The way to commemorate Jack is to get on with the work," he said.

With files from The Canadian Press