The mid-1880s brought dramatic changes in Edison's life. The first of these changes was the death of his first wife, Mary Stilwell, on August 9, 1884. Stilwell died at the age of twenty-nine, leaving Edison a widower at thirty- seven years old. Since he was still fairly young and possessed of a large personal fortune, he was quickly barraged by offers of "sympathy" from young women. The one who caught his eye was Mina Miller, a nineteen-year-old from a well-off Boston family. They met in the winter of 1885 and were married on February 24, 1886.

Mina Miller was a more assertive woman than Mary Stilwell and proved to be an invaluable companion to Edison. To occupy herself during her husband's long absences, she was active in the community. She also raised their three children–Madeline, Charles, and Theodore–in their new house in West Orange, New Jersey.

1886 was also the year Edison opened his new research laboratory in West Orange. Having outgrown the Menlo Park facility, Edison set about building a three-story building with an attached powerhouse comprising more than 50,000 square feet of floor space. The new facility had an emphasis on manufacturing and business as opposed to invention. These new directions complemented the turn of Edison's career. Still, important new inventions came out of the West Orange facility, such as the Kinetoscope and the dictating machine. Edison also perfected the phonograph and the electrical light system at West Orange.

Patent battles and competition with George Westinghouse temporarily slowed Edison's research on electrical light systems, but competition spurred his research on the phonograph. Because it had yet to provide much income and was still widely considered to be a toy, Edison had let the phonograph languish. But Alexander Graham Bell, distraught that he had not invented one first, saw great market potential in the device. In 1885 he and two of his colleagues applied for a patent on their invention, the "graphophone." The graphophone depended heavily upon Edison's phonograph technology.

Bell then approached Edison with a proposition to jointly market an improved phonograph. Edison, furious, set his energy to improving the phonograph. He produced several new models in the early 1890s and searched for a dependable power source that would make the device useful for the home market. He found the perfect match of consumer demand and high quality in 1896, when he began marketing a forty-dollar spring-motor phonograph, and sales skyrocketed into the early 20th century.

Less successful were Edison's forays into the ore-milling business. Edison first became interested in ore-milling in 1880. In the course of developing his electric light system, he invented and patented a magnetic separator for iron ore. His hope was to develop a competitor to ore mines for the east coast market. He set up plants as early as the summer of 1881 but did not devote himself fully to the project until January 1889.

Unable to attract investors to the project, Edison financed his own mines. The most promising site was at Ogden on the border of New Jersey and Pennsylvania. Edison moved there for five years to work on the project and sunk some $3 million into it. It was a massive undertaking, dependent upon a complicated system of ore-separation. It also used an intricate procedure of conveyer belts and assembly that influenced Henry Ford when he built his Model T business.

Unfortunately, the bottom fell out of the iron ore market just as Edison was preparing to put his product on the market in 1891. The Panic of 1893 had weakened businesses and prices dropped across the board. In addition, new deposits of pure iron ore were found in 1892 in Minnesota, further ruining Edison's chances. The eleven-year-long debacle drained Edison's personal finances and came to be known as "Edison's Folly."

The 1890s were a transitional period for Edison. With so many projects and businesses, he no longer had the freedom of the lone inventor. He took a new interest in manufacturing and production, recognizing that the real profitability lay in those two elements of the invention business. For years Edison had done the inventing while his financiers and business interests made the real money. Now he determined to control his own inventions and business decisions. The West Orange facility was less romantic and dynamic than the laboratory at Menlo Park, but it fit in well with the direction of Edison's vision.

The phonograph is a good example of what happened more and more toward the end of Edison's inventing life. In order for Edison to see the profitability of one of his inventions, a competitor had to lead the way. This had very little to do with Edison's capabilities as a businessman or an inventor. In addition, sometimes he did not want to use his devices in the ways competitors were using them. Bell saw the marketability of the phonograph in the idea of a music box. Edison wanted to use the phonograph for educational purposes and resisted the idea of marketing it as a music device.

Despite his initial neglect of the phonograph, Edison quickly asserted his rights when it appeared that he would be threatened by a competitor. Therefore, when Bell began encroaching on his invention, Edison shook off his anger about the potential uses of the phonograph and set about claiming his share of the market.

The ore-milling fiasco is an unfortunate chapter in Edison's inventing life, but what is remarkable is the way he bounced back afterwards. In 1897 he even established an ore-milling syndicate in London. And he recognized a potential market in one of the by-products of ore-milling–cement. In June 1899, soon after the closing of the Ogden plant, he founded the Edison Portland Cement Company. The business was the fifth largest cement producer in the United States by World War I.