Over time, federal money was set aside and bonds were issued allowing the roads to be paved.

Early on, Iowa's registered routes were marked with hand-painted signs created by the group maintaining the highways.

Today, Iowa's highway markers are compliant with standards set forth in the Manual on Uniform Traffic Control Devices.

At the turn of the 20th century, roads in Iowa were suited for horse and buggy and ill-suited for automobiles.

In 1904, less than 2 percent, or just over 1,000 miles (1,600 km) of public roads in Iowa had been improved with gravel or broken stone.

[2] At the time, roads were merely dusty dirt trails when dry, and quagmires of mud when wet.

[1] In 1913, the Commission separated from Iowa State College and gained control over county and local transportation officials, who were responsible for road construction and maintenance.

Each organization chose their colors and designed route markers to guide motorists along the way.

Iowa renumbered some primary roads in 1926; marking them with a unique number as to not duplicate the new U.S.

[5] These two new roads also made travel easier between Iowa's two most populous cities, Des Moines and Cedar Rapids.

The study committee hired two consulting firms to find the physical and financial needs of the primary highway system for the next twenty years.

In its final report to the 59th General Assembly, the study committee recommended:[9] The study committee urged caution on immediately adopting their report, instead recommending to adopt the findings over time.

On January 1, 1969, many highways in Iowa were renumbered, largely creating the numbered routes which remain today.

In 2002, the Road Use Tax Fund Committee (RUTF), a mix of city, county, and state transportation officials, met to review and recommend changes to Iowa's public road system.

The bill was passed by the Senate and House and was signed by Governor Tom Vilsack on May 23, 2003.

[12] Over 600 miles (970 km) of state highways, mostly short spur routes and segments bypassed after new construction, were turned over to county or municipal governments on July 1, 2003.

[13] Senate File 451, codified as Iowa Code §306.8A, instead created a fund for the maintenance of newly transferred highways.

Today, the primary highway system represents over 8% of the total 114,000-mile (183,000 km) public road miles in the state.

Interstate Highways in Iowa are signed with, compared to current MUTCD standards, an older style blue and red shield which features smaller numbers, wider striping, and the state's name on every shield.

County roads running primarily east and west assigned letters (from north to south) A through J.

County roads running primarily north and south are assigned letters (from west to east) K through Z.