Built in 1842 by traders George Simpson, Matthew Kinkead, Robert Fisher, Jim Beckwourth, and others, El Pueblo stood on the north bank of the Arkansas River at a long-established crossroads on the international boundary between Mexico and the United States, where the adobe fort traded guns, powder, beads, and trade cloth to customers on both sides of the border; with a peak population of about 150 men, women, and children, it felt like a semi-permanent settlement, but uneven reputation and disappointing profits led its proprietors to depart by 1848, and after a deadly Ute attack in 1854 it was abandoned for good. Soon after its 1860 founding, the town of Pueblo emerged as a center of industry with one of Colorado's deepest industrial bases and richest ethnic fabrics, drawing immigrants to its steel mills, smelters, and factories so that by 1900 more than half its residents were immigrants or first-generation Americans; known as the Pittsburgh of the West, it shared labor strife and bustling ethnic neighborhoods with northeastern factory towns, survived a devastating 1921 flood, and rebuilt. In the post-Civil War cattle trade, roughly a quarter of the hundreds of thousands of Texas steers driven north each year traveled the Goodnight-Loving Trail through this area, helping grow Colorado's cattle population from a scattered handful in 1860 to more than a million by 1880; in 1866 Charles Goodnight and Oliver Loving pioneered the first cattle trail from Texas to Colorado by driving 2,000 longhorns nearly one thousand miles, and Goodnight later settled west of here at Rock Canon Ranch and brought 30,000 head into Colorado. Colorado's frontier also developed as a heavily urban and industrial region, with mills, ore refineries, packing houses, canneries, and assembly plants rising quickly and by 1900 producing metals, farm machinery, beer, sugar, and cigars at a per capita manufacturing rate equal to Ohio's, while later aerospace and computer firms brought high technology to the Front Range. Among the state's most important companies, Colorado Fuel and Iron, created by merger in 1879, became the largest steel producer west of the Mississippi and one of the ten largest in the world; by 1904, backed by the Rockefeller and Gould families, it was Colorado's largest employer with 17,000 workers and its heaviest taxpayer, controlling quarries, mines, smelters, railroads, workshops, land companies, and banks throughout the West and providing a framework for Colorado's growth through its vast steel output and financial reserves.