Iowa 100 begins at a semi-directional T-Interchange with US 30 / US 218 in southwest Cedar Rapids. The road heads northeast along a freeway that roughly outlines the western city limits. It crosses the Cedar River about before it intersects with Edgewood Road NE at a single-point urban interchange. The road heads east towards I-380. At I-380, the mainline of Iowa 100 passes high above the interstate. Collector-distributor lanes for each highway intersect at an intermediate level between the freeways. East of the volleyball interchange, the C-D lanes of Iowa 100 intersect Center Point Road NE before rejoining the mainline at the end of the freeway. Continuing east, Iowa 100 passes the Rockwell Collins complex on the north and the studios for KGAN-TV on the south. It enters a shopping district centered around Lindale Mall. Just east of the mall, the highway intersects U.S. Route 151 Business, which runs along 1st Avenue. South of 1st Avenue, Iowa 100 leaves Cedar Rapids and enters Marion. The highway turns to southeast briefly and then straightens out to the east. It roughly marks the southern extents of Marion as the only neighborhoods lie north of the highway. It continues slightly northeast and then east again and ends at an intersection with US 151 and Iowa 13 on the eastern edge of Marion.
History
Iowa 100 was designated in the early 1980s after the southern end of Iowa 150 was relocated to Vinton. It originally followed the length of Collins Road NE in Cedar Rapids from I-380 to 1st Avenue. A plan to extend the route west of I-380 to Edgewood road was completed in 1986. In 1996 an extension was constructed eastward, through southern Marion, to US 151 / Iowa 13. Envisioned as 1960s as a bypass of Marion, the route extension served as a development corridor for the city by providing access to its southern limits. Planning for the extension of Iowa 100 from Edgewood Road NE to US 30 / US 218 in western Linn County was seen as controversial. The Linn County Conservation Board noted environmental concerns to areas such as the Rock Island Forest Preserve. Construction nonetheless began in the early 2010s and was completed on December 12, 2018.
