She has also raised a motion to the Scottish Parliament to congratulate the Stranraer Development Trust on their efforts over the past three years to regenerate the former harbour master's office.
The centre aims to establish a tourism focal point for visitors to the town that will showcase the wealth of attractions to experience in Stranraer, the Rhins and the wider Galloway area.
It will also promote local businesses, produce and crafts, as well as providing volunteering opportunities and space for community groups to showcase their activities.
Ms Harper said: “It was great to meet one of the project officers Amanda Horberry to hear directly what is planned and how the building will be a hub for the community.
"It is already showcasing the history of the area, as well as what is on offer, including local artists work.
“I want to congratulate all members of the community who have been instrumental in allowing this centre to open and I look forward to continuing to support the hub.”
Fellow South Scotland list MSP Colin Smyth has also welcomed the opening of the Gateway to Galloway.
Mr Smyth was chairman of Dumfries and Galloway Council’s economy committee when it agreed to a £3.5m regeneration programme for Stranraer.
He said: “I recall as chairman of the economy committee leading bids for the funding that resulted in the repairs and extension of the harbour master building and it’s great to see that investment now being put to use by housing the new centre.
"It will be an invaluable facility for visitors to the area and tourists, while also helping to promote the area to the wider community in Dumfries and Galloway and beyond.
“Stranraer and the wider Wigtownshire area has a wealth of brilliant and beautiful places to visit and I can’t wait to see the centre for myself and make the most of what it has to offer.”
A new Rhins Active cycling initiative runs every Sunday from the centre at 10.30am to help with physical and mental wellbeing.