Technology has changed the world in many ways, but perhaps no period introduced more changes than the Second Industrial Revolution. From the late 19th to early 20th centuries, cities grew, factories sprawled and people’s lives became regulated by the clock rather than the sun.

“It was a tremendous transformation of people’s lives,” says Joshua B. Freeman professor of history at Queens College and author of Behemoth: The Making of the Factory and the Modern World.

Rapid advances in the creation of steel, chemicals and electricity helped fuel production, including mass-produced consumer goods and weapons. It became far easier to get around on trains, automobiles and bicycles. At the same time, ideas and news spread via newspapers, the radio and the telegraph. Life got a whole lot faster.

It was an era when industrial growth created a class of wealthy entrepreneurs and a comfortable middle class supported by workers who were made up of immigrants and arrivals from America’s farms and small towns.

“People are coming from rural backgrounds who are used to self-directing their work, which is organized around the seasons and light,” Freeman says. “Now they are working in a factory that is clock-regulated and unchanging.”

For many, the shift from rural to factory life was grueling—especially for children.

When social activist Jane Addams threw a Christmas party at the group home she had just founded in Chicago’s slums in 1889, she passed out candy to the impoverished girls who lived there. She was surprised when they refused. The girls said they worked long hours in a candy factory and couldn’t stand the sight or smell of it.

“We discovered that for six weeks they had worked from seven in the morning until nine at night,” Addams later wrote, “and they were exhausted as well as satiated. The sharp consciousness of stern economic conditions was thus thrust upon us in the midst of the season of good will.”

The first factories were built in the 18th century, with British textile mills that spread to the United States, during a time known as the First Industrial Revolution. Then innovations in production line technology, materials science and industrial toolmaking made it easier to mass-produce all kinds of goods that remade the American family and physical landscape.

Factories produced sewing machines for home use, steel girders for skyscrapers and railroad tracks that cut through the plains and mountains.

Long-distance transportation networks connected by rail, steamship and canals opened new markets for farmers, factory owners and bankers who could bring America’s natural resources to a global marketplace. For the first time, goods from the American heartland could be shipped long distances, eliminating the need for local bartering systems.

Railroads were largely responsible for this great burst of economic production, according to Richard White, a Stanford history professor and author of Railroaded (2001). The iron chariots also changed the human and natural environment of the West, and of course, led to conflicts with Native Americans who had lived there for generations.

“If a Western Rip Van Winkle had fallen asleep in 1869 and awakened in 1896, he would not have recognized the lands that the railroads had touched,” White writes. “Bison had yielded to cattle; mountains had been blasted and bored. Great swaths of land that had once whispered grass now screamed corn and wheat."

Railroad lines expanded from 35,000 miles in 1865 to 254,000 miles in 1916. Yet after World War I, the railroad would be replaced by the automobile. With his emphasis on vertical integration of parts and assembly line manufacturing, Henry Ford was its king. At its peak, the Ford Motor Company factory in Michigan employed 40,000 workers under one big roof.

While some historians quibble over the exact boundary between the First Industrial Revolution, which began in the mid-18th century, and the second, which started around the mid-19th century, a primary difference is that the second saw the beginning of mass production in manufacturing and consumer goods.

Household items like soap, butter and clothing that used to be made at home started being made in factories as well. And factory workers—including women—then had the money to buy these products.

At the same time, all kinds of goods became standardized for the first time, according to Priya Satia, professor of international history at Stanford University. For example, industrial standardization marked an evolution in the arms industry, says Satia, author of Empire of Guns: The Making of the Industrial Revolution.

“You could produce all the parts of a gun and assemble any set and make a gun,” Satia says. “The advantage is if you are out in the field and something goes wrong, someone can send you that part and fix it without having to redo the entire gun.”

The changing world of the Second Industrial Revolution also led to fears by social critics about the loss of freedom, autonomy and independence that is replaced by boredom, repetition and toil, according to Freeman. Early 20th-century films like Fritz Lang’s sci-fi dystopia “Metropolis” or Charlie Chaplin’s assembly line comedy “Modern Times” capture this fear of the factory worker as a human robot.

“Ford is a great hero,” Freeman says, “but the other side of the coin is a nightmarish vision of the factory as Satan’s province.”

The Second Industrial Revolution ended just before World War I, historians say. It has been followed by the Third Industrial Revolution in which digital communications technology and the internet changed how we transmit information, do business and interact with each other.

Some argue we are now entering a Fourth Industrial Revolution, in which robotics, artificial intelligence, autonomous vehicles and biotechnology are changing our concepts of both life and consciousness. The trajectory of this phase of human development must wait for future historians to write.