The modern world imagines that the invention of electricity was greeted with great enthusiasm. But in 1879 Americans reacted to the advent of electrification with suspicion and fear. Forty years after Thomas Edison invented the incandescent bulb, only 20 percent of American families had wired their homes. Meanwhile, electrotherapy emerged as a popular medical treatment for everything from depression to digestive problems. Why did Americans welcome electricity into their bodies even as they kept it from their homes? And what does their reaction to technological innovation then have to teach us about our reaction to it today? In Dark Light, Linda Simon offers the first cultural history that delves into those questions, using newspapers, novels, and other primary sources. Tracing fifty years of technological transformation, from Morse's invention of the telegraph to Roentgen's discovery of X-rays, she has created a revealing portrait of an anxious age.