History of Macadam Road
By Curt Cunningham

Macadam Pavement

Macadam is a type of pavement composed of broken stones of small dimensions, the largest not exceeding 2.5 inches in diameter. The pavement is bound together into a compact mass similar to concrete, but with no matrix other than stone dust or screenings. Macadam was invented around 1820 by Scottish engineer John Loudon McAdam. A road paved with macadam might be more properly called a "broken-stone" road as the pavement closely resembles a gravel road.

The macadam method of road building uses a layer of well drained and compacted subsoil to support the load weight of the roadway, while the top layer acts as a wearing surface built only to shed water. Macadam road construction was based on this practice and was used worldwide. The top layer of a macadam road is mostly made of asphalt and rocks, and some builders used other ingredients to help deter road wear and add traction to the surface. Nowadays asphalt is made synthetically, but true asphalt in its natural state was originally found in only one place in the world, in a pitch lake on Trinidad Island.

Macadam was primarily used on the main highways leading into population centers where there was a moderate volume of travel. It was not an economical form of paving for city streets, and it was usually too expensive for county roads other than the main highways. Macadam became popular in the 1910's as the increasing use of automobiles caused many places to convert their roads to harder and smoother road surfaces.

On July 21, 1906 an engineering firm of Chicago, the E. R. Thomas Motor Company conducted a series of tests near its buffalo plant to see if macadam was better than brick for paving roadways. The final report was that while macadam was best for speed, and under ideal conditions, for comfort, it was found less desirable than brick for practical everyday conditions.

There were 2 types of macadam pavement; one was a water-bound mixture which was suitable for horses and wagons but not for autos. The other type was asphaltic macadam which was better for autos but not for horses and wagons.

In 1907 the Washington State Highway Department said that the advent of the automobile brought new problems to the road engineer. Under horse traffic the dust caused by the horses remained on the road until a shower or a watering cart washed it back between the stones, and the iron-tired vehicles acted as rollers on the road. The automobile was originally hailed as a great road preserver, as it was thought that the rubber tires would cause no wear in themselves and the weight of the car would help compact the stones.

This may have been true in the early days of the automobile industry, when the cars ran at low speeds, and not very far at that. But it was found that the heavier and faster cars running at high speed which seldom required the services of the plow team to get back to town, that the water-bound macadam would not stand the strain. The dust caused by the horses' hoofs and the iron tires was spread over the surrounding landscape, and in a short time the road had gone to pieces.

The engineers had to choose to either build a road with water-bound macadam which would withstand horse traffic, or build one to withstand automobile traffic using tar or asphalt macadam. The engineers were unable at the time to figure out how to build a cheap road which would stand both kinds of traffic. But it was found that using the more expensive asphalt macadam it was far cheaper in the end, than building the old style road and seeing it disintegrate in a few years.

Included in the King County road packet for County Road #57 (also known as the "Beach Road") which was established in 1879, which ran from Seattle to Allentown and terminated at Renton, had the following undated and unfinished letter about the history of macadam pavement in the state of Washington;

"Hard surfaced roads began with the use of the macadamizing system, the first roads being Road #57 (Beach Road) about 1890. The increased use of the automobile and the necessity for smooth roads resulted in important highways bring improved for such use. Aside from macadam, the first hard surfaced roads were of brick, which had first been used in Seattle in 1893. About 1908 the West Valley Road to the Pierce County line was paved with brick, with other brick roads following both north and south of Seattle. There seem to have been disadvantages in the use of brick for automobile traffic, and concrete having......." This is where the letter writer ended the story.

Macadam Road

In the summer of 1901, James Clark petitioned for a county road to be built from Allentown, across the Duwamish River and continue south to Renton Junction, where it would connect with County Road #8 also known as the White River Road which ran south to Kent. His petition would be granted and the road was designated as County Road #622 or the James Clark Road. The 3.22 mile road was completed by March of 1902.

On February 2, 1902 it was reported that the macadam road extending from South Seattle to Georgetown was nearing completion and was to be opened by March 1, 1902. The road was built by King County and paid out of the general fund at a cost $1.07 per lineal foot. This connected Seattle with the James Clark Road and the teamsters were greatly pleased with the new road. The contractors, Smythe and Howard, were several months behind due to bad weather which had stopped work for a time in January. They had to pay a forfeit of $2.50 a day for 6 months. The race track people at South Park were trying their best to persuade the county to pave the road another mile south, which they took under consideration.

The drawbridge over the Duwamish river was completed in 1903 between Riverton and Allentown. It was known as the Riverton Draw bridge and was about 250 feet long and made of cedar and fir. The pier was in the middle and the bridge could swing 90 degrees to allow steamers to pass by. On the Riverton (west side) was a wooden approach that had an entrance on the south side and the north side which connected to the road that led to the Riverton Interurban tracts. This road was abandoned in 1919.

On February 14, 1906 work began by United States Engineer A. E. Loder on a sample mile of macadam road which was to be built by the U. S. Public Works Department. This mile of road began at the drawbridge in Allentown and follows 42nd Ave. S. north as it curves around the river and becomes S. 115th Street. This sample mile of macadam pavement was to show King County the efficiency of macadam in preventing mud. On March 21, 1906 bids for the construction of the sample mile which was to be constructed under U.S. Government supervision was called for by the King County Commissioners. If the experiment proved successful this method of paving was to be followed by the county on other macadam roads. The sample mile was officially known as the "U. S. Macadam Road."

On April 10, 1906 it was reported that the entire Rainier valley was upset over the announcement made by County Commissioner Abrams that there was little hope in extending Rainer Blvd. to Renton that year. His excuse was that it cost $13,000 to build an experimental macadam road in the Duwamish valley. On August 14, 1906 the contract for construction of the mile of macadam road to connect the new government road with the county road near the Meadows race track was awarded to Price & Bell for a sum of $10,270.

The sample mile must have been a success as on December 11, 1906 there was a call for a macadam paved highway between Tacoma and Seattle. The following year on June 1, 1907 a contract was awarded to pave Road No. 1, known as the James Clarke road, with 2.88 miles of macadam. The cost of the project was $37,832.57 which comes out to $12,519.93 per mile. Then on August 6, 1907, a contract was awarded to the Tacoma Bridge Co. for a bridge over the Green River at Renton Junction. The bridge was completed in December, 1907 for a cost of $36,057.49.

At the north end of the U. S. Macadam Road, over the trolley tracks some of the survey maps between 1906 and 1908 show a wooden over-crossing. It only appears on maps between 1906 and 1908 and I could not find anymore information on this structure at this time.

On May 13, 1913 the Seattle-Pierce County Road was established. The road began at the south line of the City of Seattle, and ran in a southerly direction over the Pacific Highway to the north boundary of Pierce County. 

Macadam Road is Bypassed

After 5 short years Macadam Road was becoming obsolete. The road was narrow and had a steep grade and many curves. Beginning in 1914 plans were being drawn up for the construction of a new level highway between Riverton and Renton Junction following the Interurban trolley. 

On August 4, 1914 the Riverton-Renton Junction County Road #1004 was established. This was a section of the Seattle-Pierce County Road. This new road began at the intersection of Dale St. and Road #70 in Riverton, which today is the intersection of S. 128th Street and E. Marginal Way. This new road followed S. 133rd east toward the river and turned southeasterly along the west side of the trolley line and followed it to Renton Junction. This section of road was approximately 3 miles long and included a bridge over the Duwamish river about a mile downstream from the old bridge at Allentown and a new bridge at Renton Junction.

By 1916 County Road #1004 and the new bridges over the Duwamish River were completed. The Pacific Highway was then routed onto this new alignment, and Macadam Road was bypassed. The new road eliminated the dangerous and deadly trolley crossing at Allentown.

Between 1917 and 1919 concrete paving began on the Riverton-Renton Junction Road and cars were detoured back over Macadam Road.

After the paving project was completed in 1919 the Riverton drawbridge was closed to traffic, and 8 years later in 1927 the structure was removed.

In 1924 the Pacific Highway was rerouted over the "Highline" road which runs through Federal Way, Des Moines, and South Park. This is when the Riverton-Renton Junction Road was bypassed. Today this road is known as Interurban Avenue.