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M-6, or the Paul B. Henry Freeway, is a 19.7-mile-long (31.7 km) east–west freeway and state trunkline highway in the United States that serves portions of southern Kent and eastern Ottawa counties south of Grand Rapids, Michigan. Although the freeway is named for Paul B. Henry, local residents and the press continue to use the original name, South Beltline as well on occasion. The freeway connects Interstate 196 (I-196) on the west with I-96 on the east. M-6 also provides a connection to U.S. Highway 131 (US 131) in the middle of its corridor while running through several townships on the south side of the Grand Rapids metropolitan area in Western Michigan. Each end is in a rural area while the central section has suburban development along the trunkline.
The freeway was originally conceived in the 1960s. It took 32 years to approve, plan, finance, and build the freeway from the time that the state first authorized funding in 1972 to the time of the ribbon-cutting ceremony in 2004 that opened the South Beltline to traffic. The project cost around $700 million or around $35 million per mile (approximately $22 million per kilometer). Initial construction started in November 1997, with the first phase opened in November 2001. The full freeway was opened in November 2004. The first phase of construction was completed in asphalt, while the second and third phases were built in concrete. The project was built with two firsts: the first single-point urban interchange (SPUI; /ˈspuːiː/) in Michigan, and a new technique to apply the pavement markings, embedding them into the concrete to reduce the chance of a snowplow scraping them off. In advance of the opening of the freeway to traffic, the Michigan Department of Transportation (MDOT) allowed the public to walk or bike the South Beltline in an open-house event called the "Southbelt Shuffle".