In his travels to the western frontier in the early 1830s, American writer Washington Irving characterized the Cross Timbers as "forests of cast iron." Irving used this colorful metaphor to emphasize the toughness of the vegetation that he encountered—a nearly impenetrable forest of stunted oak trees. We now recognize that the unique forest that Irving experienced was actually vast in extent and covered portions of what would later become three states. Seen on a satellite photo, the Cross Timbers run in a generally north-south direction across a large area that includes portions of southern Kansas, eastern Oklahoma, and north central Texas. Although they do not compose a single forest, but a complex mosaic of forests interspersed with prairies, the Cross Timbers constitute an impressive geographical feature.
In this book I shall build further on Irving's apt cast iron metaphor, which has meaning far deeper than even he might have imagined. If cast iron owes its character to the ore that is wrested from the earth, forged by heat, and quenched by cold, then the trees of the Cross Timbers themselves may be seen in light of both the geological and climatic forces that shaped them—namely, the ancient iron-rich rocks through which their roots search for water and nutrients, and the extreme climate that molds the shapes of their tortured trunks and limbs.
More than a century after Irving wrote of the region, ecologists confirmed that the distinctive trees of the Cross Timbers are well adapted to the scorching, sometimes droughty summers and to the occasional, bitter winter cold snaps that are a fact of life in this part of the south central United States. In their remarkable ability to endure in the face of rapid human settlement in the late twentieth century, the Cross Timbers are almost as durable as Irving's metaphorical cast iron. Even in areas of suburban growth around Fort Worth and Arlington, Texas, remnants of the eastern Cross Timbers have survived as shade and ornamental trees. As a testimony to the endurance of this unique habitat, the name "Cross Timbers" has now become popular for businesses and other enterprises in the area.
As I will make evident, the Cross Timbers have a rich history in relation to human exploration and settlement. Existing at both the margins of the western prairies, and the forested woodlands of eastern North America (fig. 1), the Cross Timbers compose a unique ecological zone that, in human terms, has provided habitat and sustenance on the one hand and has served as a reminder of the harshness of the environment on the other. Like many before and after him, Washington Irving was ambivalent about the Cross Timbers. He recognized that they could provide fuel and shelter, but he also cursed their resilient, unyielding countenance. Given Irving's early experiences with the bountiful—and more easily traversed—forests of his native New York State, his ambivalence was understandable.
In retrospect, Irving's ambivalence was also prophetic, for the Cross Timbers were often spurned in the mid-nineteenth century for the more attractive prairie-and-oak openings. Although the Cross Timbers would help sustain hunters and settlers, most of those who settled in the area actually sought the forests' edges, the oak-savannah ecotones that were a mixture of prairies and trees, and which provided a variety of both "open" and "closed" landscapes. The Cross Timbers in some sense thus represented the least desirable aspects of forests: they impeded one's travels and, at the same time, offered relatively few rewards.
My first exposure to the Cross Timbers occurred in the mid-1950s, while on a transcontinental road trip that took my family across Texas. Even at twelve years old, I marveled at the changing landscapes we traversed. Like Irving, my first experience with forests had been in the lush, mesophytic woodlands of New York State, and so I judged all forests by that standard. As our automobile rushed westward through east Texas, trees seemed to become fewer and smaller in the vicinity of Dallas-Fort Worth. We had reached the magnificent open prairies, those sweeping, open seas of grass punctuated here and there by a tree, or a few trees, that stood out as if islands. In our rush westward into the prairies, however, we also traversed two narrow but distinctive belts of trees that at first seemed little more than scrubby second-growth forests. And yet, a closer look suggested that many of these trees were not young, cutover growth at all, but rather mature trees that had been stunted. Their twisted and gnarled trunks conveyed a sense of age, and their height—perhaps only thirty feet at best—implied the hardship that results from tribulation. They reminded me of the scrub oaks that somehow managed to grow on the poorest, sandiest soils of Long Island, New York, where little other tree growth could be sustained. I would indeed learn years later that two of the common oaks of the Cross Timbers, the post oak and blackjack oak, are native to and found on sandy soils from southern New England and Long Island all the way to the Cross Timbers at the edge of the great American West.
Like other westbound travelers through Texas, we soon crossed through these dwarfed forests, which were, in effect, the last flatland forests that we would encounter until reaching the Pacific coast some 4500 miles farther west. We discovered what ecologists and geographers have known for more than a century: that these wooded areas—the Cross Timbers—represent the last of the forests as one crosses the continent from east to west. The Cross Timbers thus provide a glimpse of the ecological challenge that all vegetation faces at the margins of the great American West and Southwest. West of the Cross Timbers, in fact, forests are found only in the riparian river valleys or in the more well-watered mountains.
More than 40 years after first experiencing the Cross Timbers, I moved to this very region of Texas, and I wanted to learn more about it. In fact, my forested backyard in Arlington represents remnants of the Cross Timbers, and I found myself following that wonderful advice given by naturalists: to really understand nature, start in your own backyard and work outward from there. In addition to observing the Cross Timbers hereabouts, I read widely into the subject. Over the years I had encountered a rich but somewhat scattered literature on the Cross Timbers, of which Edward Everett Dale's The Cross Timbers: Memories of a North Texas Boyhood (1966) remains a personal favorite since I first read it in 1970. Carolyn Foreman's The Cross Timbers (1947), long out of print, provided an excellent guide to the historic literature but did not emphasize the region's ecology. After an extensive search of the literature, I soon found that relatively little had been published on the Cross Timbers' natural history in relation to human settlement. After collecting files of information about the region's history and ecology, I set about writing The Cast Iron Forest in hopes of telling the story of this unique region of North America. I have attempted to include those numerous writers who commented upon the region in published works, some popular, some obscure. It should be noted from the outset that some of the early writers called the region The Cross Timber, which implies singularity, while later writers, myself included, use the term Cross Timbers. This more or less plural usage corresponds to our understanding of the region not as one solid forest, but rather as a series of forested areas that coexist with the prairies. Yet I use the term Cast Iron Forest as a title in recognition of the region's singularity among American regions.
Although The Cast Iron Forest is, to my knowledge, the first book to be published about the region's unique natural environment—and that environment's relationship to the human experience of settlement—it builds upon a rich literature. Much of what I write here is based not only on several years' fieldwork, but also on several excellent studies of the area's vegetation, history, folklore, and geography that are cited throughout. It also builds upon a group of unpublished but fascinating studies, many of them master's theses or doctoral dissertations, completed at universities over the years.
A word is in order about the term "natural history" in this book's subtitle. By it, I mean a basic treatise on some aspect of nature (especially the "natural development of something," as the dictionary defines it). But I also use another time-honored definition of natural history: "the study of natural objects, especially in the field, from an amateur or popular point of view," as the dictionary also defines the term. Because I have a deep respect for the history of science, wherever possible I have used original descriptions and illustrations to help tell the story of the Cross Timbers. On occasion, those materials do not agree with what we know today; that is what makes them so delightful, for they reflect the limitations in knowledge at any particular time. Overall, however, I have been impressed by how cumulative our knowledge of the region has been, and so I use even the speculative materials to show that the Cross Timbers are a changing geographical, scientific, and cultural frontier. Because this book is both a natural and a cultural history, by definition it must also treat the changing human perceptions of the region.
As a historian and geographer, I have also made use of another type of primary source documentation that has rarely been used in relation to the Cross Timbers—namely the many historic maps that for more than two centuries have depicted the Cross Timbers forest as a distinctive part of the region's geography. In doing so, I build upon Charles Oliver May's ambitious 1962 geography thesis—the first cartographic study of the region. In addition to cartographic materials, many other written records, such as journals, diaries, and historic reports, also help tell the story of the Cross Timbers. We shall see that no two cartographers have agreed on the exact distribution of the Cross Timbers. Even the map used in this introduction—based on biogeographer A. W. Kuchler's approximation of when the forest existed—is controversial. That very divergence of opinion about the Cross Timbers, while frustrating, adds to their mystery.
In addition to consulting several hundred maps of the Cross Timbers, I used the landscape itself for clues to determine the character and distribution of the forest. As a geographer, I have also studied the Cross Timbers in the field and from the air, observing first-hand the relationship between its vegetation and the region's geology and settlement. The general lack of existing photographs of the Cross Timbers (likely due to the fact that the area is not especially photogenic—certainly not as much so as the Texas Hill Country, or Palo Duro Canyon, or Oklahoma's mountainous "Kiamichi Backwoods" country) required me to photograph them extensively in all seasons. Capturing it on film made me ever more aware of the region's subtle but neglected beauty. Surprisingly, this book also appears to be the first published work to include extensive photographic coverage of the Cross Timbers. I hope that the results of my efforts—this book entitled The Cast Iron Forest in recognition of Washington Irving's encounter with the region more than a century and a half ago—conveys my sense of wonder about the Cross Timbers. I hope, too, that it convinces the reader that the Cross Timbers are a fascinating and significant part of North America's natural and cultural history.