The last kegs will be filled on Thursday after brewing company Lion announced plans to close the facility in 2020.

"Unfortunately, due to excess brewery capacity across Australia, the tough decision was made to close the site late last year," Lion Supply Chain Director Ian Roberts said.

"During this transition, Lion has done its best to care for and offer a raft of support to the West End team as each of them faced this period of change.

The West End leadership team and their staff have been exceptional in recent months, Mr Roberts said.

"While understandably disappointed by this decision, they have continued to focus on brewing to the highest standard and keeping the beer flowing for their loyal SA customers and consumers."

Lion will move production of West End beer to other breweries in its network and has pledged to maintain the same recipe.

It said the original West End Brewery tower building had also been heritage-listed and the company was working with Heritage SA to ensure its preservation as part of the site redevelopment.

A significant museum of artefacts at the site were also being catalogued and sorted and would be donated to the Library of SA and other local historical and cultural institutions.

When the closure was first announced it was thought about 90 jobs would be lost, though Lion said about a third of its workforce in SA, those involved in sales and sponsorship roles, would stay on.

Premier Steven Marshall said the end of beer production was a very sad day for South Australia.

"West End has been on that site for a long period of time. It's an iconic South Australian business and we're very sad that it will be leaving," the premier told reporters on Wednesday.

Australian Associated Press