Carved in Stone

Brooke Wisdom

August 1, 2010

H is for Highway

From cow paths to freeways, we seldom appreciate what went into America’s highway system.

‘hī-wā (noun) – There ys a dyfference bytwypte an hyghe waye and a bypathe, for the hyghe waye ys large and commune to all… (The Myroure of Oure Ladye, 1530, p. 140)

By Bill Langer

In The Cow Path (1895), New Hampshire poet Sam Walter Foss describes how long ago a calf made a path through the woods. The path became an established animal trail, followed by human travelers, then horses, then wagons, until:

“The years passed on in swiftness fleet,

The road became a village street;

And thus, before we were aware,

A city’s crowded thoroughfare.

And soon the central street was this

Of a renowned metropolis;

And men two centuries and a half

Trod in the footsteps of that calf.”

As we travel along ancient cow paths, whether from our home to work or across the country, we seldom appreciate what went into creating America’s highway system.

During 1806, money was appropriated to construct the National Road (a.k.a. the Cumberland Road) extending from Cumberland, Md., to the nation’s interior. The panic of 1837-1840 essentially curtailed appropriations for the road which, at that time, extended through Ohio and Indiana into Illinois.

It was not until the beginning of the 20th century and the advent of the automobile that the true value of roads became appreciated. The Post Office Appropriation Act of 1912 and the Rural Road Act of 1916 made federal funding available for rebuilding the National Road. The Federal Highway Act of 1925 provided federal aid for the construction of the numbered federal highway system, and the National Road was realigned and incorporated as U.S. Route 40, part of one of the first new interstate highways.

Following World War II, deterioration of highways and the realization that highways are critical for national defense resulted in the passage of the 1956 Federal-Aid Highway Act that created the Interstate Highway System, and pushed new highway construction and design standards. On Aug. 2, 1956, Missouri became the first state to award a contract for work on the new Interstate system (specifically Interstate 70, then U.S. 40), the Mark Twain Expressway located in St. Charles County. East of the Rocky Mountains, much of Interstate 70 follows U.S. Route 40, the previous route of the National Highway.

By 1991, the Interstate System was 99 percent finished with a length of 36,147 rural miles and 6,397 urban miles of highway. Interstate 70 through Glenwood Canyon, Colo., which opened for traffic on Oct. 14, 1992, was one of the final pieces of the interstate system to be completed.

The Interstate Highway System launched an unprecedented demand for aggregate. USGS Bulletin 1594 (Langer, 1988) gives approximate values for tons of aggregate used in the construction of various types of highways and secondary roads. Applying those values to the Interstate Highway System and assuming that all the Interstate was of four-lane construction (an obvious underestimation), construction would have required about 2.9 billion tons of aggregate.

During the period 1956-1991, about 776,000 miles of non-interstate highways and 460,000 miles of secondary paved roads were also constructed, collectively consuming about 18 billion tons of aggregate. The bottom line is that between 1956 and 1991, about 32 percent of U.S. aggregate production was used for highway construction.

All by itself, Interstate 70 probably used about 150 million tons of aggregate. Not too bad for an old cow path.

Bill Langer is a geologist with the Mineral Resources Team of the U.S. Geological Survey and can be reached at 303-236-1249 or via e-mail at


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