From A Dictionary of Music and Musicians

By John Alexander Fuller-Maitland, George Grove

Steinway in a few years turned his attention to piano-making, and in 1839 exhibited a grand and two square pianos at the State Fair of Brunswick. Seesen being in Hanoverian territory, the foundation of the Prussian 'Zollverein' in 1845 brought Steinway's hitherto flourishing business to a standstill, and the revolution of 1845 destroyed it entirely. The course of events now induced Steinway to leave Germany, and in April 1849 he emigrated to New York, whither his family, with the exception of Theodore, the eldest son, followed him the next year. For three years the father and the three sons, Charles, Henry, and William, worked in different New York piano factories. In March 1853 they agreed to unite and start in business on their own account, and the firm of 'Steinway & Sons' was established. In 1855 they exhibited a square piano in which the American iron frame principle of a single casting was combined with a cross or overstrung scale, forming the foundation of the so-called 'Steinway system,' which, as applied to grand pianos, attracted great attention in the London International Exhibition of 1862. Both Charles and Henry Steinway dying in 1865, Theodore, the eldest son, disposed of his business in Brunswick and became a partner of the New York firm. Their spacious concert-room there was built and opened in 1866. About this time the Steinways began to make upright pianos, and their instruments of all kinds shown at Paris in the Universal Exhibition of 1867, not only gained them success, but became models for Germany, to the great improvement of the German make and trade. Henry Steinway, the father, died in 1871. We may quite from the New York Encyclopedia of Contemporary Biography the summary of his life: 'By virtue of his abilities and his inborn strength of character, he, an orphan boy, became one of the greatest manufacturers in his special industry, not only of his own country, but of the world.' Theodore and William Steinway are now (1882) the senior partners of the firm. In 1875 they opened a branch of their business in London, to which a concert-room is attached, and in 1880 another branch establishment in Hamburg. [A.J.H.]

Source: Fuller-Maitland, John Alexander and George Grove (1883). A Dictionary of Music and Musicians (A.D. 1450-1880). Macmillan. 709-11.