It all began when an advertisement appeared in the then Maitland Daily Mercury on June 15, 1918 calling on all returned soldiers to attend a meeting in St Paul's Parish Hall.

In less than a year, the sub-branch would receive its official charter on June 1, 1919 and have more than 120 members.

Vice president Fred Goode said it was an important milestone for the organisation.

"We received our charter on June 1 in 1919, so we are marking it with a lunch on Sunday," he said.

"We want to take an opportunity to thank our members, the women's auxiliary and community for its support.

"We want to celebrate 100 years in Maitland. We serve the whole community.

"The sub-branch has a very rich history."

Throughout its life, the sub-branch has moved throughout the city but provided a valuable service in the community.

The first annual meeting of the West Maitland Sub-branch of the Returned Sailors and Soldiers Imperial League was held at the West Maitland School of Arts on July 7, 1919.

The sub-branch's current home, 3 Bulwer Street, was opened by its oldest serving member Tom Taylor in 1999.

Now, a century later, the Maitland RSL Sub-Branch has 122 full members and two associate members.

Mr Goode added the local branch was always keen to welcome new younger members.

"They tend to join later ... but they are missing out on some great activities and their wives being part of the auxiliary," he said.

According to its mission, the branch aims to 'assist and be a fortress of solitude for current and ex serving Australian Defence Force/Allied Personnel, and to assist the community in the commemoration of important dates in Australia's military history'.

The centenary lunch, which will host more than 100 guests from across the state, will be held at Club Maitland City on Sunday, July 14.