The lake and Millennium Plaza in Lake Oswego
Oswego Lake is the feature that gives the city its name, and it is not an ordinary public lake. This page sticks to what official and reference sources say, and points to the City for current rules.
Millennium Plaza Park
The City of Lake Oswego describes Millennium Plaza Park as a delightful urban park in the heart of the city, overlooking Lakewood Bay. It has a pergola, a fireplace, a reflecting pond and a paved plaza. The park is at 1st and Evergreen. The City lists restrooms, picnic tables, food concessions, accessible parking and facility rentals. It is where the Saturday farmers market is held, and the City's page also lists Movies in the Park in July and August and Sunday Moonlight and Music concerts.
George Rogers Park
The City's parks page describes George Rogers Park as a 26-acre community park at 611 S. State Street, with ball fields, a playground, tennis courts, a memorial garden and Willamette River access. It is one of the two venues of the Festival of the Arts each June.
Oswego Lake
Wikipedia describes Oswego Lake as a former channel of the Tualatin River, enlarged by the Missoula Floods and later raised by a concrete dam built in 1921. It is about 3 miles long and completely surrounded by the city. The lake was once called Sucker Lake and was renamed Oswego Lake in 1913. The Lake Oswego Corporation, owned by lakefront property owners and easement associations, claims ownership and controls access. Wikipedia reports that who may use the lake has been argued in court for more than a decade, with rulings in 2022, 2024 and 2025. Because that is still moving, check the City of Lake Oswego for the current access rules rather than relying on this page.
The City's swim park
The City's Lake Oswego Swim Park is open to Lake Oswego residents from July 1 to August 31, daily from 1 p.m. to 6 p.m., weather permitting. Residents show proof of residency, and non-residents may enter only with a resident for the whole visit. There are capacity and two-hour visit limits. The City's page says Lake Grove Swim Park is owned and run by the Lake Oswego School District.