There were wild rumours of nuggets weighing up to 18kg being unearthed in the St Arnaud region, and thousands rushed to its hills, gullies and creeks in hope of changing their fortunes.

The little town in the Northern Grampians was described by some as a "gold town with a golden future".

That era, as captured by local historians, still gleams in the town's main street more than 150 years later.

Napier Street, with its two-storey pubs, ornate iron verandas and original post office, court house and fire station, will be celebrated as part of Main Streets Of Australia Week.

This week's national movement encourages towns to support their local businesses, while also recognising the crucial social function of main streets.

"The very essence of most people is they want to belong," the campaign's spokeswoman Alli Price told AAP.

"If we don't have main streets or town centres anymore then that feeling of belonging is gone, that connectedness is gone."

Many towns taking part across Queensland, South Australia, Western Australia and Victoria will showcase their heritage.

About 100 kilometres west of St Arnaud, Horsham's theme is "What was and what is", featuring the history of the Wimmera Coffee Palace, which is now a nightclub.

During its construction in 1918, The Horsham Times described it as "a splendid addition to the town", featuring Queensland maple panelling and a spacious veranda.

Ballarat architect and heritage consultant Wendy Jacobs says preserving historic main streets is both atmospheric and practical.

"It's a sense of place, a sense of identity that this is home," she said.

"Then there's the tourism, people like to walk back in time and see it. And verandas are useful. They're shady in summer and keep the rain off in winter."

Main street businesses can also look to history to improve trade, says NSW heritage consultant David Scobie.

"David Jones, Grace Brothers and Myer used to train window dressers. It was a very skilled trade in preparing shopfronts and changing merchandise regularly," he said.

"Nowadays, you're lucky if you see anything in the window. I sound like an old British sitcom, but we've lost a generation of people who are skilled and trained."

He says lighting, street furniture and murals enliven tired main streets, and one unique shop can lead a change.

"It becomes more than a coffee shop, more than a dress shop,'' Mr Scobie says.

"Everybody meets there, and they chat about everything."

Towns involved in the campaign are turning their main streets into live art spaces, open libraries and markets throughout the week.

Ms Price hopes it reminds people to gather in their town centres, especially after periods of pandemic isolation.

"Main streets really are the heart of the community," she said.

Australian Associated Press