From History of the Piano by Ernest Closson

Excerpt from chapter three, entitled "The Piano"

...the most famous of American piano manufacturers was to be Heinrich Steinweg (who was born in Wolfshage in the Harz Mountains in 1797 and died in New York in 1871). After beginning his career in Brunswick as an instrument maker, then as an organ builder, Steinweg decided to build pianos, constructing his first instrument in 1835 in Seesen, Harz. The political disturbances of 1848 having brought business to a stop, Steinweg sent his son Karl to America to try out the territory. The result of this inquiry was favorable and Steinweg embarked for America in 1850 with his sons Karl, Heinrich, Wilhelm and Albert, leaving his son Theodor as the chief of his business in Brunswick. In 1858 Theodor was joined by Friedrich Grotrian and the firm subsequently became known as Grotrian-Steinweg. Meanwhile, Heinrich Steinweg and his four other sons settled in New York, working with local manufacturers in order to study the methods of American piano making. In 1853, anglicizing their name, they founded the firm of Steinway and Sons. Its prosperity was as extraordinary as it was rapid. Steinway and his sons had naturally begun with square pianos which they were soon making at the rate of fifty a week. But they wasted little time with this superannuated type, and quickly turned to the concert grand which they enriched with improvements...

Source: Closson, Ernest (1947). History of the Piano. New York: St. Martin's Press, 102.