Drive down almost any highway across the U.S., and you can't help but notice all the Segmental Retaining Wall projects that are being constructed. And when you look at these beautiful and functional walls, some questions come to mind: Where did these walls come from, and why are they so popular? Many years ago, Segmental Retaining Wall Systems (SRW) were conceived as modular units that could be stacked upon each other, fastened together with some type of mechanical interlock. The earliest versions of these walls were simply wet cast, molded concrete, while modern units are produced on state-of-the-art block and paving stone machines, yielding high quality and extremely cost-effective systems. More than twenty-five different SRW systems are currently being marketed throughout North America today, each offering a different type of design and look. Available in different colors, shapes, sizes and structural configuration possibilities, some systems have a definitive corner design, while others utilize serpentine curves to change direction. Most wall systems have a set back design that affects the batter of the wall, but some allow designers to build vertically in situations where total land utilization is critical. No matter what particular system you prefer, each shares the same basic characteristics and function: a flexible, mortarless, dry stack system that utilizes a variety of interlocking features and does not need a concrete foundation as it is constructed on a compacted road base footing. These interlocking features come in the form of metal rods, pins, clips, rear lips, male and female molded channels and locator extrusions. All SRW systems perform in the same manner and operate on the same engineering principles. Uniformly applied to particular system specifications, these principles allow for the design and construction of an individual SRW system. SRW systems did not just jump onto the drawing boards and become an instant success, but have gradually realized great acceptance through the extraordinary efforts of the different wall system developers, their local manufacturers, and many Landscape Architects. This collective commitment to the belief that SRW systems really do work has created an enjoyably high level of success today. Landscape Architects have long recognized the design advantages that SRW systems have to offer, but DOT authorities have responded a little more slowly, needing confidence that the new systems really work. Recognizing the advantages of SRW systems-- tremendous cost savings, fast construction, resistance to seismic damage, freeze thaw stability, design flexibility, longevity and functional beauty for all to appreciate-- DOT authorities across America have finally recognized their functionality and reliability, and are taking full advantage of them. Landscape Architects who wish to explore the many SRW options available to them may contact the author, LASN's Associate Editor/Hardscape Specialist at 708-553-1174 or by email at paverlen@aol.com.