Life in post-World War I Mercedes was flourishing in what was called the Roaring Twenties during a vibrant time of economic prosperity in the United States.

Mercedes was in its third decade of existence in the 1920s. By all historical accounts, the city was booming as it was transformed into a vital agricultural and commercial hub in the young and emerging Rio Grande Valley. Mercedes was a growing town with a population of nearly 3,500 residents by 1925.

Horses, carriages and early automobiles shared Texas Avenue, the city’s main street then, as it is now. Vintage autos parked diagonally along downtown sidewalks. On Texas Avenue, Mercedes could boast of having drug stores, hardware shops, clothing stores and a two-story Hidalgo County Bank & Trust. The largest grocery store of that time in the Valley – Garcia Bros. Grocery Store – drew shoppers from neighboring towns.  

Then in late May 1929, everything changed, and life would never be the same for Mercedes and the Valley as a whole. A severe and historic flooding event occurred when local torrential rains combined with similar inundations upstream pushed massive volumes of water down the Rio Grande. Mercedes sits roughly seven miles from the river with its offshoot Arroyo Colorado located just one mile from the city.

It was all too much for a town that was already known as the “Queen City of the Valley.” Accounts from late May 1929 report that “parts of the town were completely submerged under as much as 14 feet of water.” Half of the homes in Mercedes were left underwater and floodwaters completely inundated the downtown district and local agricultural fields.

“The region completely lacked modern flood control infrastructure, reservoirs, or comprehensive levee systems at the time,” states an account from the Texas State Historical Association. “The swollen river easily burst its banks.”

Flood Exposed Lack Of Controls

Photographs of the great 1929 flood are sparse.

The few that can be found show rooftop flooding in Mercedes and neighboring La Feria. Another vintage photo shows floodwaters lapping up to the front windows of a two-story building on the intersection of Texas and 2^nd streets. One account cited on a Facebook RGV historical page states, “Records detail families marooned on their rooftops waiting for rescue as water covered the surrounding countryside.”

This seminal flooding event of 1929 altered how regional, state and federal officials would deal with catastrophic types of floods. More than $3 million in bonds were approved by area voters to build levees from Donna to Brownsville. It marked the first steps toward the modern-day floodways and related drainage channels seen today throughout the RGV.

Subsequent flooding events in the early 1930s demonstrated the need to coordinate flood controls with Mexico.

“The 1929 flood starkly exposed the dangers of relying on individual, uncoordinated local levees built strictly on the American side of the river,” says a Texas State Historical Association document.

In September 1932, the International Boundary Commission proposed the construction of floodways on each side of the river. Both countries agreed to do so. The U.S. side alone would include 300 miles of river and floodway levees, improvements and control works that would take nearly 20 years to complete, with 1951 being the finishing year.

One of the products of that massive project was the RGV’s floodway system that passes through Mercedes. It was in this era that the Lower Rio Grande Flood Control Project established its headquarters in Mercedes in 1932. The “Queen City” with its strategic Mid-Valley location became the focal city for coordinating a comprehensive network of control structures, interior floodways and river levees spanning from western Hidalgo County to the Gulf of Mexico.

And the starting point for it all was the great 1929 flood, now largely forgotten in Mercedes, but that would prove to be a pivot point in the city’s history.

- Ric Cavazos