The View From Wisconsin

11. Interstate 516, Savannah, GA. The W.F. Lynes Parkway on the western edge of Savannah, GA is one of several Interstate highway spurs that travel in both directions from the mainline Interstate – that is, it crosses over the two-digit interstate or intersects and runs concurrently with its parent before traveling off in another direction. The southern spur serves Hunter Army Air Field southwest of Savannah, while the northern spur follows the route of US 80 west to Garden City. The seven-mile-long bypass is somewhat of an oddity, as it contains two 90-degree turns on each side of I-16, making it look like a "Z" on the map. The southern spur connects with the Southwest Bypass, which circles around the west side of Hunter AAF to GA 204. Like other highways in Georgia, I-516 is overlapped by GA 21 for its entire route. US 17 and US 80 join the freeway at exit 3, with US 17 North heading off with I-16 East while US 80 continues on with the Lynes Parkway to exit 7A. US 80 actually runs alongside the last mile of the freeway before heading south and then west, paralleling I-16.
12. Interstates 55, 64 and 70, East Saint Louis, IL. Saint Louis, MO, is considered to be the Gateway to the west by many. It also is a focal point for four Interstate highways that cross or converge on the city. Three of them meet at the south end of the Jefferson National Expansion Memorial (the Gateway Arch), and crosses the Poplar Street Bridge over the Mississippi River to East Saint Louis. This convergence is only one of two instances of three mainline, two-digit Interstate highways sharing the same stretch of road for an extended length. The section extends for just over three miles, until it reaches Interstate 64's eastern section. When a new bridge over the Mississippi is constructed up-river, this alignment may be changed. MoDOT actually claims that I-44 follows the triplex across the Poplar Street Bridge, ending at the state line over the river. This would seem to indicate that the Missouri section of the Poplar Street Bridge is actually a "quadruplet" of four Interstates; however, signage on I-44 eastbound ends at its interchange with I-55 a mile to the southwest.
13. Interstate 170, Saint Louis, MO. Known better to locals as the Inner Belt Expressway, I-170 is one of only three Interstate "spurs" that cross their mainline highway west of the Mississippi River. The heavily-traveled highway runs north to south through the Saint Louis suburbs of Hazelwood, Berkeley, St. John, Overland, University City and Clayton, from Lambert International Airport and I-270 to Interstate 64. The spur was supposed to continue south to I-44 and along River des Peres to I-55 near Bella Villa; the municipalities in south St. Louis County, however, voted the plan down. The freeway right of way was sold off, and a Target store sits right at the end of I-170.
14. Interstate 76 (Colorado to Nebraska, and Ohio to New Jersey). When AASHTO decreed an end to lettered Interstates, it caused some states to renumber sections of freeway to designations already in use in other states. Interstate 76 is such an example; the section from Arvada, CO (northwest of downtown Denver) to I-80 west of Ogallala, NE (I-76 is only in Nebraska for a little over a mile) was changed from I-80S. I-76 was already in use as a freeway designation in the east, having replaced the same I-80S designation from the greater Akron, OH area to the New Jersey Turnpike northeast of Philadelphia, PA. I-76 was actually first designated in the east in 1963 from Camden, NJ to Pittsburgh, PA. I-76 was later routed south into Philadelphia and the Walt Whitman Bridge, ending at I-295 in New Jersey. As the eastern I-76 only touches I-80 once (outside of Youngstown, OH), it would not make much sense for the two routes to be connected via a duplex signing with I-80. The I-76 designation is appropriate for both sections of freeway, as the state of Pennsylvania is well known as being the location of the signing of the Declaration of Independence in 1776, and Colorado became a state in the US Centennial year of 1876.
15. Interstates 35W and 35E, Minneapolis/Saint Paul, MN. This is the only other lettered freeway pair in the US, and it has the same issues as its other pair in Dallas/Fort Worth. The difference here is that it would be relatively easy to re-route I-35 through both cities; I-35 could take the route of I-35W from Applewood into Minneapolis, then multiplex with I-94 east into Saint Paul, then head north on the route of I-35E to Lino Lakes. The remaining sections could be renumbered I-235 and I-435. However, the Twin Cities, like many siblings, do not want to "share" I-35. Unlike its sister Interstate in Texas, I-35W is the longer of the two sections in Minnesota at 41.78 miles, due to its three "step-overs" in downtown Minneapolis.
16. Interstate 394, Minneapolis, MN. When the freeway system was being planned in the Twin Cities in the 1950's, it was decided that US 12 (also known as Wayzata Boulevard) would be turned into a freeway from 3rd Avenue North in Minneapolis out towards St. Louis Park and points west. Originally, only the spur from I-94 east to Washington Avenue in downtown Minneapolis was planned as I-394. The extension to the west and I-494, constructed and opened in the late 1980's, was later added to the route. I-394 was one of the last major Interstates to be completed in the Twin Cities region. The section from I-94 to I-494 is the first route in Minnesota to have a toll "lane"; MNDOT converted reversible high-occupancy vehicle (HOV) lanes into toll lanes requiring a MNPASS transponder for electronic toll collection. The tolls started to be charged in May of 2005. The east spur may become an off-ramp to a new Minnesota Twins ballpark, planned for a parking lot just off the end of the freeway at Washington, near the Target Center.
17. Interstate 180, Hennepin, IL. As you are driving down I-80 through the central plains of Illinois, you come upon a strange freeway interchange: I-180, just east of Princeton, IL. This freeway spur heads south for about 10 miles, takes a hard left and crosses over the Illinois River into Hennepin. There doesn't seem to be any reason for the freeway to exist, until you realize that Interstate highways have a secondary purpose: defense. LTV Steel was a major defense contractor, located in Hennepin – which is why the freeway was built in the 1960's (it opened in 1969). This is the only case of an Interstate highway built for private enterprise in the US. There is a possibility that the freeway could be extended to Peoria on a bypass of IL 29, running alongside the Illinois River, but for now it is a very low-traffic freeway – since LTV Steel went bankrupt in 2002 and the plant was closed.
18. Interstate 84 (Oregon to Utah and Pennsylvania to Massachusetts). This is another case of a lettered Interstate changing numbers. The western section of I-84 was formerly I-80N, traversing from Portland to I-15 in Utah, before re-designation in 1980. I-84 actually violates the AASHTO rules about numerical placement of Interstates, as it intersects with I-82 north just east of Umatilla Army Air Field and Depot in northeast Oregon. The eastern section was already in place between Scranton, PA and the Massachusetts Turnpike. The section of I-84 between Hartford, CT and the Massachusetts Turnpike was originally signed as I-86, and I-84 would have instead diverted along what is now I-384 towards Providence, RI. That section was never built past Bolton, CT.
19. Interstates 90, 94 and 39, central Wisconsin. From the time it opened in 1961, the section of I-90 and I-94 from Wisconsin Dells (later from Tomah) to Madison was the only co-signed Interstate in the state of Wisconsin. In the 1990's, as US 51 was being bypassed to the south in Illinois, a decision was made to do the same to the stretch of US 51 from Portage to Merrill, WI. In 1999, the US 51 freeway in Wisconsin was upgraded to an Interstate designation; since the section in Illinois had already been designated as I-39 (and there was no other number available in the corridor), the section was renumbered as such. A year later, the stretch between Cascade Mountain and the Cherry Valley Interchange in Rockford was re-signed with Interstate 39 signs. This made the 33.5 mile section from Cascade to the Badger Interchange with I-94 east and WI 30 the longest concurrent stretch of three "mainline" Interstates in the US. I-39 and I-43 are slightly out of alignment with the Interstate grid, as they are located east of three higher-numbered freeways (I-45, I-49 and most of I-55).
20. Interstate 43, Wisconsin. Originally the northern spur of the north-south freeway in downtown Milwaukee, I-43 was originally planned to connect downtown Milwaukee (at the current Marquette Interchange) to the unbuilt Belt Freeway, near the Milwaukee-Ozaukee County line. It would have then connected with a northern leg of the Lake Freeway (also unbuilt) that was planned to head north towards Michigan. I-43 was eventually completed near the Lake Michigan shoreline to Sheboygan, Two Rivers and up to Green Bay. Its northern terminus is at US 41 on the northwest side of downtown Green Bay. In 1990, the I-43 designation was placed on the WI 15 Rock Freeway on the southwest side of Milwaukee, extending I-43 to its current length of 191.55 miles to its new terminus at Interstate 90/39 on the east side of Beloit. The I-43 highway continues west into Beloit on WI 81, as the WI 15 designation was reassigned elsewhere in the state (northwest of Appleton). I-43 misses the Illinois border by 2.2 miles on I-39/90. I-43 and I-94 are the only two Interstates that cross, intersect or multiplex with all but one of the other signed Interstates in Wisconsin. The lone Interstate not touched by the pair is I-535, the Blatnik Bridge, in Superior.