Bowers Rock State Park is a state park located in Linn County, Oregon, about a mile west of the city of Albany. It is located along the east bank of the Willamette River, and is approximately 570 acres, or a little less than a square mile.
Bowers Rock State Park is unimproved, and has no facilities other than a sign at the entrance. The entrance itself is a gravel private road that does not allow motorists, so the only land access to Bowers Rock State Park is by foot or bicycle. There is no signs mentioning the park on the road outside, and the Oregon State Parks website does not mention it if you search a list of state parks. (There is, if you look in the right place, a pdf file with a single page, showing a map of the park.)
As far as I can tell, there are two reasons that the park is undeveloped: the first is that it is surrounded by private property, and that even the innoucous uses of a state park involve traffic and noise, and road construction. In addition, the park is located next to the river in a floodplain, and construction of certain facilities might be difficult, and require regular maintanence. In addition, the parks isolation probably makes it better habitat for many types of wildlife.
Acquiring land is only the first step for a parks department. The additional challenges of developing a parcel of land in a way that is fair to neighbors, park-goers, and that preserves habitat, while also being cost-effective, is much more difficult, which is why Bowers Rock State Park is in a type of limbo.