Geography Land features See also List of Michigan state parks and geography of Michigan. The Thumb's landscape ranges from a flat sandy plain along the shores of Lake Huron and Saginaw Bay, to a gently rolling topography. This land is fertile and well suited for agriculture. The most unusual geographic formation is a rugged glacial moraine, known collectively as the Hadley Hills, which extends in a northeasterly direction through the center of The Thumb, from the southwestern portion of the peninsula. All counties except for Lapeer border the Saginaw Bay or Lake Huron. The places with the highest elevation are all associated with the Hadley Hills, and are located in Lapeer County, they are: Pinnacle Point, at , Kerr (Cemetery) Hill, at , both in Hadley Township, Mt Christie, at , in Metamora Township, and a point near Mayville, reaching up to above sea level. The lowest point in the Thumb region is the shore of Lake St. Clair, at a low of above sea level. Huron County is very flat. It has large fields that were used for agriculture and now are the sites of numerous wind turbines to generate electricity. The "tip of the Thumb" is Pointe Aux Barques, between Port Austin and Grindstone City. Marlette is called the "heart of the Thumb," because of its central position on the peninsula. Major rivers The Thumb has many waterways. Cass River has many branches, one of which flows into the Shiawassee River in the Shiawassee National Wildlife Refuge at less than from where the Shiawassee merges with the Tittabawassee River to form the Saginaw River The Pinnebog, Shebahyonk, and Pigeon rivers all rise in the center of Huron County and empty into the Saginaw Bay. St. Clair River, connects Lake Huron to Lake St. Clair, and is the farthest east border in Michigan. It forms a low impression in eastern St. Clair County, and has a delta at its mouth (North America's largest freshwater delta), which includes Harsens Island and Walpole Island, Ontario. Ferries cross the river at Algonac and Marine City, these being international border crossings. Black River rises near Minden City and flows into the St. Clair River at Port Huron. The Black River forms a basin in Sanilac County, and northern St. Clair County. The north branch of the Flint River lies in northern Lapeer County. It rises near North Branch. The southern branch flows through