Bridges and culverts can be great indicators of when a highway was built and by whom it was built. In California, there are a few different styles of railing which can be used to put a relative date on a particular bridge when they don’t have date stamps on them. Other indicators may be used when the bridge rail has been modified or even replaced by modern rail. Styling elements on the superstructure vary depending on age. Older bridges tend to be more ornate than more modern structures. This page will serve as a guide to these styles and help to increase understanding of what goes into the design of these bridges.
Old US 99 still has some gems remaining in the Coachella Valley. On of these is a set of railroad overpasses dating from 1936 and 1956 (56-09R/L). These structures may be replaced in the near future, so I took the opportunity to take some photos of them before they are gone. Each structure is different in type of construction as well as design. The 1936 structure retains its solid concrete railing, something somewhat unique for the period. Most bridges of that era had a more open and arched railing. This bridge has a very much “Art Deco” styling which still looks quite nice today. The bridge carried all US 99 traffic until 1956, when US 99 was upgraded to an expressway through this area. At that time, a second bridge for southbound/eastbound traffic was built. The 1956 span, a steel girder structure, is longer than the 1936 span. This may be due to plans, at that time, to eventually replace the 1936 bridge with a newer and longer span. While these plans may have been initially thwarted by the construction of I-10 on a new alignment east of here, the bridges days are indeed numbered with the reconstruction of the Jefferson St interchange and eventual realignment of roadways in this area.
These bridges are located on Indio Blvd just east of the Jefferson St interchange on I-10 in Indio, CA. Enjoy them while they last.
Sometimes when a road gets realigned, a portion of the old roadway remains as an access road. This was the case when a small section of Rialto Ave (Arrow Highway/Route) was realigned in 1961 between Rancho Ave and Mt Vernon Ave. This realignment left behind a short span from the 1940’s. The bridge doesn’t have a date stamp nor is it still in the county bridge logs, so an exact date is tougher to find. Still, this bridge has a fine example of bridge rail from that era and is a good find.
Concrete is a very durable material. It has many uses, though for our purposes – roadway surfaces, curbs, and sidewalks. Local roadways, such as concrete city streets, won’t be covered in this post. Bridges will be covered in a later post. This durability allows us to get either a relative date of when a roadway was paved or built to an absolute date when we find a date stamp.
- Style of Paving
As technology has evolved, so has concrete paving. The first concrete paving along State Highways was 10-12′ wide, usually not reinforced with steel. These roads were paved in one single slab of concrete. Roadways of this style were paved from around 1910 to 1915. After 1915, wider paving was used and was generally reinforced. Wider paving ran from 15′, 18′, and a “full” 20′. These are usually referred to as “Single Slab Paving”.
Sometime around 1923, longitudinal joints were added to the concrete paving. This created a “Twin Slab” roadway. This style persists today, though greatly changed. Early Twin Slab roadways had fewer expansion joints running across the lane. After around 1926, this problem was worked out by adding more frequent joints. By this time, each lane was a “standard” 10′. This standard remained until the late 1940’s when lane width started to widen to 12′.
- Date Stamps
Contractors, either by requirement or pride, usually stamp the concrete roadway, curb, or sidewalk with a date stamp. These stamps vary in location, size, and information. Date stamps marked either the beginning or end of a days paving. As such, the stamp tended to be located near an expansion joint. A general rule with date stamps is “find one, you can find the rest”. This is mostly about the location. Some stamps are in the middle of a lane, some are to the side of a lane. The orientation also varies with stamps. The information contained in these stamps also varies. Early stamps just have the contractor and the date. Later stamps added the engineering station. Without going into too much detail, at this time, about engineering stations, the “zero” point is at the beginning of a road section or project. With little exception, I have had little success in finding a date stamp on Single Slab roadways. Twin Slab roadways are much better with stamps.
Using date stamps and styles as a guide, you can easily date a roadways construction to within a few years. There are other methods you can use, but these aren’t covered here. Some will be covered in later posts. Stay tuned for more posts. Bridges, Road Signs, and more will be covered in the future. If you have any questions, please post a comment or send me a message.
When looking for old highways, there are many clues you can use to help discover where old highways ran. This will serve as a partial guide to finding those clues and figuring out the history of a roadway in California.
When you are looking for clues if a roadway you are on is an old State Highway, there are a few things to look out for. Depending on the age and location, look out for Right of Way monuments. In California, these are small concrete blocks with a C on the side of them, facing the roadway. They tend to be at the fence line along roadways, at the same distance as the utility poles, or further out. How much they stick out also varies. Some are just a few inches above the ground where others are about a foot high. Look out for these monuments at the beginning or ending of a curve usually about 50-100′ from the centerline of the roadway (or former centerline).
Other clues tend to be tougher to spot but can be very subtle in appearance. Roadways that were formerly paved with concrete instead of asphalt are usually cracked in a very specific way if the asphalt is old enough. Expansion joints in the concrete, potholes exposing the old paving, or a defined crack running near the roadway edge usually give this away. Older concrete paving was either 15′, 18′, or 20′ wide. Modern roadways are usually 24′ wide, with two 12′ lanes. Look out for this concrete at curves which appear to have been straightened.
On some roadways bypassed or abandoned after 1964, old postmile markers can be found. These markers are similar to the ones on current State Highways. On a current roadway with R mileage, look for old alignments in the area. R mileage indicates a realignment that took place after 1964, which is the point of “base mileage” for California State Highways.
Abandoned roadways are tougher to spot depending on the area climate. Drier climates tend to preserve older paving better than wetter climates. In some areas, the paving itself was removed after the roadway was bypassed. I have found a few sections of roadway relatively intact, complete with old striping, in Central and Eastern California. When the pavement has disintegrated or obliterated, you can look out for areas where there is less vegetation and distinct roadway grade. Sometimes old drainage culverts and bridges are left behind with nothing but dirt grade leading to them.
In any area, make sure to take plenty of photos if you find an old alignment. You never really know when the local jurisdiction will come along and either obliterate or repave the roadway. This is fairly common in Los Angeles County as I have found. The most recent loss has been the June 1933 three lane concrete in Gorman along old US 99 which was repaved in the past couple years. Document what you find as best as you can. Doing so will help to preserve the memory of these forgotten roadways for many years to come.