Michigan Highways: Since 1997.

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M-22 & M-109 junction route signage in Glen Arbor, Michigan
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M-100 Route Marker On to Next Route:
Former M-101
Southern Terminus:    I-69 at Exit 66 on the south side of Potterville
Northern Terminus:    I-96 at Exit 86 north of Grand Ledge
Length: 12.845 miles
Maps: Route Map of M-100
Notes: M-100 is a somewhat minor state trunkline highway route running parallel to the north-south segment of I-96/I-69 on the west side of Lansing, several miles to the west (see route map). It has been earmarked for complete decomissioning (transfer from state to local control) on at least one occasion during its history, although no such plans seem to exist today.
  In "State Trunkline Needs, 1960–1980," a set of maps prepared by the State Highway Dept's Office of Planning, Programming Division in 1960 showing possible additions, upgrades and improvements to the state trunkline system over the ensuing twenty years, MSHD staff recommended the entire length of M-100—save for the one-mile segment concurrently designated with BUS M-43 along E Jefferson and S Clinton Sts in Grand Ledge—be decommissioned and turned back to local control. Oddly enough, the exact opposite happened in the ensuing decades: M-100 was retained and slightly lengthened in the 1990s at Potterville, while BUS M-43 through Grand Ledge was decommissioned in the late 1960s.
History: 1924 – M-100 traces its beginnings to a segment of highway which had been part of the route of M-16 running between Lansing and Portland on its way toward Grand Rapids. Leaving Lansing, M-16 followed Saginaw Hwy westerly into Eaton Co to Hartel Rd south of Grand Ledge, turning northerly via Clinton St, northwesterly along Jefferson St, then northeasterly on Bridge St, then northerly again via Clinton St and Hertel and Wright Rds into Clinton Co, to Grand River Ave where M-16 continues northwesterly via Eagle toward Portland. During 1924, the route of Grand River Ave running drectly between Lansing and Eagle is improved and surfaced with concrete and becomes a de facto part of the Lansing–Grand Rapids trunkline route, although not officially established as a state trunkline until the next year.
  1925 (Sept 1) – The portion of Grand River Ave between the Ingham/Clinton Co line northwest of Lansing then northwesterly toward Eagle is officially established as a state trunkline highway route and designated as part of M-16 removing it from the route west of Lansing via Saginaw Hwy (present-day M-43) and then northerly through Grand Ledge back to Grand Ledge. Theoretically, this is the genesis of the route of M-100, however evidence points to the fact that M-100 may not be posted along the former north-south segment of M-16 from Grand Ledge northerly to Grand River Ave at this time. Official State Highway Dept maps and internal documents only indicate the north-south segment of former M-100 through Grand Ledge is still a trunkline route, but don't indicate a route designation for it. Media reports similarly fail to note anything regarding M-100.
  1927 – M-100 is indicated on official State Highway Dept maps for the first time this year running along the original alignment of M-16 between M-39 (present-day M-43) in Grand Ledge and US-16/Grand River Ave north of Grand Ledge. It it was not posted prior to this, M-100 is now signed as such in the field.
  1932 – The route of M-100 is extended from Grand Ledge due southerly to Potterville:
  • (Sept 15) – The state highway advisory board approves a 9.1-mile extension to M-100 running concurrently with M-39 (later M-43) along E Jefferson and S Clinton Sts to Saginaw Hwy (where M-39 departs easterly toward Lansing), then southerly via Hertel Rd to US-27/M-78 at Potterville. The advisory board then forwards its recommendation to the State Administrative Board for consideration.
  • (Oct 29) – The 8.1 mile new trunkline along Hertel Rd from M-39/Saginaw Hwy southeast of Grand Ledge southerly to US-27/M-78/Lansing Rd in Potterville is officially established as a state trunkline highway route. The one mile of M-39 along E Jefferson and S Clinton Sts in Grand Ledge is now concurrently signed with M-100.
  1958 (Jan 20–24) – The new US-16 freeway is completed and opened to traffic on Jan 20 from just east of M-100 northwesterly toward Portland. The route of M-100 is extended by approximately 370 yards from its previous northern terminus at former US-16/Grand River Ave to a new terminus at the US-16 freeway (present-day I-96). The additional 0.2 mile of M-100 route along Wright Rd from Grand River Ave to the new freeway interchange is officially established as a state trunkline four days later on Jan 24, the same day this segment of the US-16 freeway itself is also officially established.
  1959 (Nov 13–16) – The M-43 Grand Ledge Bypass is completed and opened to traffic on Nov 13 and officially assumed into the state trunkline system three days later on Nov 16. With this, the formerly concurrent M-43 routing via M-100 into Grand Ledge becomes BUS M-43.
  1967 (Sept 29) – The concurrent BUS M-43 routing at Grand Ledge is decommissioned. M-100 now runs solo along S Clinton and E Jefferson St between M-43/Saginaw Hwy and downtown Grand Ledge.
  1991 (Dec 21) – M-100 is extended by several hundred yards to the south to meet up with the new I-69/US-27 freeway just south of Potterville as that freeway is officially completed and opened to traffic.
  1993 (Jan 12) – The 0.310-mile extension of M-100 from OLD US-27/Lansing Rd southerly to the I-69/US-27 freeway just south of Potterville is officially established as a state trunkline and transferred from city to state control. It had been marked-and-maintained as a trunkline route since the opening of the new freeway bypass more than a year prior.
Controlled Access: No portion of M-100 is freeway or expressway.
NHS: No portion of M-100 is on the National Highway System (NHS).
Memorial Highway: At present, no portion of M-100 has been designated as part of a Memorial Highway.
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