Given that IH 80 crosses the width of the state, I suspect it's about 200 miles, the width of the state. Iowa is 310 miles long.
Geography of the United States
Interstate 80 (I-80) is a transcontinental limited-access highway that runs from downtown San Francisco, California to Teaneck, New Jersey in the New York City Metropolitan Area. The second-longest Interstate Highway in the United States (after Interstate 90), I-80 is the Interstate Highway that most closely approximates the route of the historic Lincoln Highway, the first road across America. The highway roughly traces other historically significant travel routes in the Western United States: the Oregon Trail across Wyoming and Nebraska, the California Trail across most of Nevada and California, and, except in the Great Salt Lake area, the entire route of the First Transcontinental Railroad.
The United States is a country in the Northern Hemisphere, Western Hemisphere, and the Eastern Hemisphere. It consists of forty-eight contiguous states in North America, Alaska, a peninsula which forms the northwestern most part of North America, and Hawaii, an archipelago in the Pacific Ocean. There are several United States territories in the Pacific and Caribbean. The term "United States", when used in the geographical sense, means the continental United States, Alaska, Hawaii, Puerto Rico, Guam, and the Virgin Islands of the United States. The country shares land borders with Canada and Mexico and maritime (water) borders with Russia, Cuba, and the Bahamas in addition to Canada and Mexico.
Iowa Highway 92
The United States of America (USA), commonly referred to as the United States (US), America, or simply the States, is a federal republic consisting of 50 states, 16 territories, a federal district, and various overseas extraterritorial jurisdictions. The 48 contiguous states and the federal district of Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The country also has five populated and nine unpopulated territories in the Pacific and the Caribbean. At 3.79 million square miles (9.83 million km2) in total and with around 316 million people, the United States is the fourth-largest country by total area and third largest by population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The geography and climate of the United States is also extremely diverse, and it is home to a wide variety of wildlife.
Paleo-indians migrated from Asia to what is now the US mainland around 15,000 years ago, with European colonization beginning in the 16th century. The United States emerged from 13 British colonies located along the Atlantic seaboard. Disputes between Great Britain and these colonies led to the American Revolution. On July 4, 1776, delegates from the 13 colonies unanimously issued the Declaration of Independence. The ensuing war ended in 1783 with the recognition of independence of the United States from the Kingdom of Great Britain, and was the first successful war of independence against a European colonial empire. The current Constitution was adopted on September 17, 1787. The first 10 amendments, collectively named the Bill of Rights, were ratified in 1791 and guarantee many fundamental civil rights and freedoms.
U.S. Route 6 in Iowa
Iowa Highway 92 (Iowa 92) is a state highway that runs from east to west across the state of Iowa. Iowa 92 is 275 miles (443 km) long. Its eastern terminus is at Muscatine on the Norbert F. Beckey Bridge over the Mississippi River where Iowa borders Illinois and Iowa 92 meets Illinois Route 92. The western terminus for Iowa 92 is at Council Bluffs at the Missouri River where it crosses the border from Iowa into Nebraska and meets Nebraska Highway 92.
U.S. Highway 6 (US 6) is an east–west U.S. Highway which runs 319 miles (513 km) across the U.S. state of Iowa. It is signed in places as the Grand Army of the Republic Highway. Like all state highways in Iowa, it is maintained by the Iowa Department of Transportation. The route begins at the Missouri River crossing at Council Bluffs. From there, it travels east through Oakland and Atlantic, Iowa. North of Atlantic, the highway overlaps Interstate 80 (I-80) until De Soto. Between De Soto and Adel, the highway overlaps U.S. Highway 169 (US 169) before splitting off to the east towards Des Moines. Through the Des Moines area, it runs about one mile (1.6 km) north or south of the I-35 / I-80 corridor.