Hartwick Pines State Park is a 9,672 acre (39.2 km²) State Park in the US state of Michigan, located in Crawford County near Grayling and Interstate 75. It is the third largest state park on Michigan's Lower Peninsula and the state's fifth-biggest park overall. The park contains an old growth forest of white pines and red pines that resembles the appearance of all of Northern Michigan prior to the logging era.The Hartwick Pines are a 49 acre (0.2 km²) old-growth remnant of a pine grove that was withdrawn from logging by a local timbering firm in 1927. At that time, very little old-growth pine remained in northern Michigan. One of the heirs of the firm's original owners, Karen Michelson Hartwick, donated the grove, which was then 85 acres (0.35 km²) in size, and 8,000 surrounding acres (32.4 km²) of cutover land to the state of Michigan as a memorial to the logging industry.
On November 11, 1940, the Armistice Day Blizzard badly damaged the Hartwick Pines old-growth pine grove. 36 acres (0.15 km²) of old trees were destroyed by windthrow from this and other storms, leaving behind the 49 acres (200,000 m2) that remain alive as of 2007.The Michigan Forest Visitor Center opened in 1995 and is a year-round facility. The building contains an exhibit hall on the history of the forests in Michigan, an auditorium, classroom space, a bookstore operated by the non-profit Friends of Hartwick Pines and restrooms.A State Park Motor Vehicle Permit fee is charged to enter the park. Visitors are encouraged to park at the visitor center and walk an accessible trail to the big trees. The Old Growth Forest Trail to the pine grove is a loop 1¼ miles (2 km) long. The Old Growth Forest is an even-aged stand of pines estimated to be between 350–375 years old. The tallest trees are between 150–160 feet tall, and have a girth of more than four feet DBH (Diameter at breast height). These Eastern White Pine are some of the largest trees in the eastern United States.