Using Lidar to Map El Camino Real in East Bastrop County

In our article on The Old San Antonio Road in East Bastrop County, we showed that when surveyor V. N. Zively was reconstructing the route of the road in 1915, he mislabeled two streets in downtown Bastrop. We then speculated that this labeling error may have influenced his interpretation of the Old San Antonio Road. We proposed an alternate route that seemed to not only fit the geography and terrain of the area better, but also was in better accord with the history of the city of Bastrop. We now take a closer look at the route of El Camino Real in east Bastrop County using lidar data provided by the Texas National Resource Information System (TNRIS).

Map of the Old San Antonio Road in East Bastrop County

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Zively's Route from Paige to Bastrop Compared to Modern Roads

As explained in our first article on this subject, at the beginning of the 20th century, there was a road leading west out of Paige toward Bastrop. According to a 1907 map, the last dwelling on the road was five miles west of Paige. Zively placed an oak survey post, which he labeled Post #62, at that location. Present-day Highway 21 follows Zively's route from Paige to his Post #62 location exactly. Apparently, when Highway 21 was constructed some twenty to thirty years later, the road Zively followed was still in use, Highway 21 simply took it over, and the various widenings and resurfacings of the road that have taken place in the decades since have not moved the route.

For approximately the next five miles, Zively surveyed a route that ran somewhat south of Highway 21's present location. The 1907 map shows a road quite similar to Zively's, but the conformance between Zively and the 1907 map is not as exact as it is between Paige and Post #62. It is possible that since there were no dwellings on this part of the road, travel on it was less frequent. It may have degraded into a small trail, or system of small trails - one preferred by riders, another more suitable for wagons, one easier if the ground was dry, another better if it was wet, etc. It is possible that this segment of the Old San Antonio Road was not readily adaptable to use as a state highway, and why Highway 21 was built nearby instead of overlaying the old route.

Zively placed Post #63 about five miles from Post #62. The direction of the road between Posts #62 and 63 is approximately west-southwest. At Post #63, Zively turned west and crossed what is now Highway 21. He then stayed well north of Highway 21 and went further from it until he reached the northeast city limits of Bastrop. He then turned somewhat sharply south and entered Bastrop on Hill Street. He placed his next post, Post #64, in downtown Bastrop at the intersection of Chestnut and Hill Streets.

The segment of Zively's route between Posts #63 and #64 requires special scrutiny. All historical evidence points to Chestnut Street, a principal east-west street in Bastrop, as being the route of the Old San Antonio Road. The 1907 map, and other maps, show roads in the vicinity of present-day Highway 21 connecting Chestnut Street to Post #63. Zively, however, interpreted the OSR as going through the hilly terrain northeast of Bastrop and entering the city from the north on Hill Street. At first glance, this appears to be a mistake, and the reason for the mistake appears obvious when examining Zively's sketch: he mislabled Hill Street as Chestnut Street, and vice-versa. If his sources told him the OSR followed Chestnut Street, but he believed Chestnut Street was Hill Street, that would explain why he went off into the hills and approached downtown Bastrop from the north instead of from the east.

One thing we know about Zively's route between Posts #63 and 64 is that it did follow some existing roads. About 2,000 feet of it are now used by a modern street called Pine View Loop. An old road named Hoffman Road preserves approximately 1½ miles of Zively's route. There is no question that Hoffman Road existed when Zively made his survey, and the conformance between his route and Pine View Loop is too exact to be purely coincidental. The fact that these roads existed in Zively's time does not prove, however, that they were part of the 19th-century Old San Antonio Road. The first question for this analysis then, is: is Zively's route between Posts #63 and 64 a feasible interpretation of the Old San Antonio Road? Our second query is, regardless of Zively's interpretation, what is the best or most likely route of El Camino Real between Paige and Bastrop? Both of these questions can be answered with the help of lidar data.

Lidar-assisted interpretation of the Old San Antonio Road in east Bastrop County, with Zively's route
Annotated satellite photo of east Bastrop County. Background image courtesy of Google Earth.

Adding Lidar Analysis

The satellite photo above of east Bastrop County shows modern roads in yellow and Zively's route in brown. Trails, ruts, and swayles revealed by lidar data that do not follow modern roads are in light blue. As the photo shows, Zively's route from Paige to Post #62 is correct - what additional ruts or trails that exist are short and close to the main road. The photo also shows that between Posts #62 and 63, the Old San Antonio Road definitely did not follow Highway 21, but instead ran a short distance south of it. Zively's survey of this segment seems to be skewed from the lidar traces by a few hundred feet, but it follows the shape of the traces quite faithfully, and the skew could be due to our error in interpreting his survey. As we move on, however, we see that most of the ruts and swayles that still exist today rejoin Highway 21 either near Post #63 or a little west of it. Highway 21 appears to be a quite accurate representation of the 19th-century Old San Antonio Road as it approaches Bastrop and becomes Chestnut Street. Zively's crossing of Highway 21 at Post #63 and use of Hoffman Road do not appear to be justified from looking at this image.

Also note that there are two traces leading west from Post #63 - one that branches west and follows Zively's route for a half a mile, and one that continues going southwest. We have observed many instances where the placement of Zively's survey posts appears to signal ways in which the road changed significantly, such as there being a fork in it. In this case, it looks like Zively placed Post #62 where he did - in front of the last dwelling west of Paige - because that was where the "good" road ended, and it possibly started to become more of a backcountry trail. He then placed Post #63 at a point where the trail he had been following branched in two, and he chose to go west.

The set of three photos below examine the route Zively took after leaving Post #63. The top photo shows Zively's route overlayed on a lidar image, with a Google Earth roadmap also overlayed. While Post #63 is out of frame on the right, one can see the two sets of traces leading from it - the upper trace that Zively followed, and the lower trace that goes to downtown Bastrop via Highway 21 and Chestnut Street. One can see that Zively's route skips from Highway 21 to Pine View Loop to Hoffman Road.

The middle photo in the set below shows the same information, minus Zively's route. The bottom photo is an unmodified satellite image. One can see evidence in both of these photos that Zively's connection between Pine View Loop and Hoffman Road appears to have some basis. His connection between Pine View Loop and Highway 21, however, is harder to see any evidence of. In neither case are the traces as clear and well-defined as the ones leading down Highway 21 into Bastrop on Chestnut Street.

Lidar-assisted interpretation of the Old San Antonio Road in east Bastrop County, with Zively's route
Lidar images courtesy of Texas National Resource Information System. Roads courtesy of Google Earth.

The area between the west end of Hoffman Road and Post #64 has been developed for urban and residential use, so any old trails or ruts were erased long ago. A lidar examination of this area would yield no information about the Old San Antonio Road.


Lidar analysis supports our original assertion that Zively's route of the Old San Antonio Road through the hills northeast of the city is an error, and that this error was most likely caused by his confusion over Hill and Chestnut Streets. While there was certainly a Hill Street in early Bastrop that went north out of the city into the hills, and there was a road - present-day Hoffman Road - that went through the hills, these roads served principally to give people who lived in the northeast part of Bastrop County a route into the city of Bastrop. The faint indicators of trails connecting the east end of Hoffman Road to Highway 21 are most likely remnants of local trails that residents of the hill country used to access the Old San Antonio Road, not remnants of the Old San Antonio Road itself. In other words, the line Zively drew between Posts #63 and #64 depicts routes used by residents of the hills when they needed to go to Paige or Bastrop, not the main route between Paige and Bastrop, let alone the main route between Nacogdoches and San Antonio. That route is represented fairly well between Posts #63 and 64 by Highway 21. The lidar data supports Zively's route from Post #63 to Paige.

By David Carson and Darrell Hebert
Page last updated: April 23, 2019