While I am far from an expert on classical music, I do enjoy it and it strikes me that I don't know of a single American composer before Copland. So, what is the history of classical music in the first century or so of the United States? Was there anything unique about it? Did the Romantic and Nationalist musical movements extend influence across the ocean in any way? Were there any early American operas? Or was the Unied States a classical backwater with little of it's own music to speak of?
This is an area of classical music I am not particularly into, but I can tell you a little about:
Anthony Philip Heinrich (1781 – 1861). Born in Bohemia, he is frequently mentioned as the first "American composer" and full-time professional concert musician. He was not entirely self-taught (I think), but certainly had to pick up a lot of things on his own. There are a few recordings on youtube to get an idea of what he was into (IMSLP has some scores).
Amy Beach (1867 – 1944) was the first successful American female composer. She was a child prodigy and her mother was her first piano teacher. People told her to try to study at a European school, but she decided to stay and study in the US. She studied some harmony and counterpoint and was mostly self-taught after that. She was active as a concert pianist, but her (significantly older) husband wanted her to limit her public performances (see, that was not an acceptable life for a proper woman, much less a married woman), she then focused on composition (she composed big works, as well as a lot of songs). She wrote some very nice music, and will have no problems at all finding more about her music.
Edward MacDowell (1860 – 1908). He studied in European schools (Paris, Frankfurt). I think Liszt might have been present at one of his recitals. He went back to the US and became a professor of music at Columbia. He was very conservative in his tastes, and most of the musicians surrounded him considered him kind of old-fashioned. His music is very, very... Romantic. A hell of a lot of kids taking piano lessons frequently play this little piece. It has quite a charm, doesn't it? It certainly sounds like the music of a long gone time (it probably sounded dated in his days... those were crazy modern times, MacDowell was not following the trends at all).
Those are the three names I am familiar with. You might want to check the other The Boston Six.
The names I know after that time are pretty well known.
You might want to read The Cambridge history of American music.
I assumed you meant "from the US," but I can mention some composers from other parts of the "New World."
In mid to late eighteenth century New England, a rich tradition of unaccompanied four-part psalmody developed quite distinct from European trends. Composers like William Billings, Supply Belcher, Jeremiah Ingalls, and Daniel Read helped popularize the "fuguing tune," which is an item quite distinct from the fugues of Bach. The melody carried in the tenor, a fuguing tune generally begins with all four parts in rhythmic unity. The parts will generally sing together until the middle of the poetry, whereupon each of the four voices will enter in turn, staggering the text, until the parts come back together in the final phrase.
The Better Music Movement of the early nineteenth century, however, favored a more modern European style of composition, and scorned these earlier composers as "unscientific." This was not least in part because Billings and his contemporaries deliberately ignored many rules of classical harmony—parallel fifths and octaves abound, while total consonance was often ignored in favor of making each part melodically interesting.
Although banished from the classical mainstream, the early New England music flourishes to the present across various shape-note traditions, most prominently amid the folk hymnody of The Sacred Harp, a four-shape tunebook first published in 1844 that remains in continuous widespread use across the American South and as of the last few decades, increasingly the rest of the world. Early New England music is also increasingly popular with classical ensembles focused on "early music."
Check out this recording of the 1787 major key tune Ocean, made by Sacred Harp singers in Texas. As is traditional among shape-note singers, they sing "on the shapes" (the solfege) before launching into the text around 1:00. Also check out Daniel Read's earth-shattering Calvary, a splendid minor key tune.
My "Chronicle of America" (Longman, 1989) mostly seems to mention classical music in the context of European composers/performers:
"Most popular opera is "Poor Soldier", New York City, December 1785. The American Company, just back from Jamaica, has scored a big hit with The Poor Soldier. In fact, the opera's run of 18 performances at the John Street Theater has set a new record. The work is of a pot-pourri nature, a collection of today's popular tunes. But one of them, A Rose Tree, has become a great favorite. The troupe went into exile after Congress passed the Anti-Theater Act in 1774. With the passage this year of a similar measure by the city of Philadelphia, the only two places where theater performances are any longer legal are New York and Maryland".
"New York, March 3, 1794. James Hewitt writes music for opera Tammany or The Indian Chief".
"Joseph Jefferson stars on New York stage, New York City, Dec. 20, 1796. This has been a busy theatrical season, from the long-awaited New York debut of the celebrated English actor Joseph Jefferson in February to the opening yesterday of Victor Pellisier's opera Edwina and Angelina here... April in Boston saw the mounting of The Archers, an opera with music by Benjamin Carr and libretto by that energetic literateur William Dunlap. Viewers were sympathetic to a plot based on William Tell's struggle for freedom. Of special note was Why, Huntress, Why? sung to a woman who pleads for the right to fight alongside the men. One of the nation's most popular songs this year was written by the English organist-composer George K. Jackson, who no sooner was settled in Virginia than he penned the romantic One Kind Kiss".
"Boston musicians found Philharmonic, Boston, 1810. Boston's first family of music is bringing beautiful sound to a city still reluctant to indulge in frivolous arts. Johann Gottlieb Graupner, who first played in a Prussian army band, is host to Boston's 12-member Philharmonic Society on Saturdays at Graupner's Hall. Partly social, it often attracts a big audience. Graupner's wife, Catherine Comerford Hillier, an English opera star, often sings, and he shifts between clarinet, oboe, double bass, flute and piano".
"Boston, 1817. Handel and Haydn Society gives first complete performance of Messiah.
"Kentucky rings with sound of Beethoven, Louisville, Kentucky, 1817. The hills of Kentucky are ringing with the sounds of Beethoven, at least near Louisville. The Bohemian musician Anthony Heinrich recently conducted a Beethoven symphony here, reportedly the first performance of a Beethoven symphony anywhere in America. The number of the symphony was not noted, but it was noted that Heinrich had found players equal to the task. Heinrich is a composer, too, and has written some music inspired by the American landscape".
"New York, Nov.29, 1825. "Barber of Seville" opens at the Park Theater".
"New York City, 1826. Tenor Manuel del Popolo Vincente Garcia rents Park Theater in attempt to start permanent Italian opera company here".
"Philadelphia, June 4 1845. Leonora premieres at Chestnut Street Theater; first opera by an American to reach the stage". (Doesn't say who wrote it).
"New York City, 1847. Astor Place Opera House, largest to date, seats 1,500; opening production is Verdi's Ernani".
"New Orleans, November 19th, 1860. Adelina Patti, nation's foremost opera star, makes debut at French Opera House".
"Boston, May 1868. First Triennial Festival held, with "first truly satisfactory performance in this country" of Beethoven's 9th".
"Vienna's Strauss conducts in Boston, June 17, 1872. Johann Strauss is the star of the World's Peace Jubilee and International Music Festival that began tonight, conducting his Blue Danube waltz with an orchestra of 2,000 players. Strauss, who arrived June 13 from Austria on the steamship Rhein, is one of Europe's most famous composers, best known for his waltzes. Ten concerts are being given, ostensibly to celebrate the end of the Franco-Prussian War. The massive event was organized by the famous American band leader P.S. Gilmore, who favors musical performances with maximum instrumentation. He is also known as the composer of When Johnny Comes Marching Home. Eclectic international music is the theme of the jubilee. The hall where the concerts are being performed seats thousands of people, and Strauss is being paid $1 per seat to conduct".
Doesn't tell you much, except what kind of thing was popular.
After further research (read: Google) Leonora was written by William Henry Fry.
Not the earliest, but check out this guy: http://en.wikipedia.org/wiki/William_Grant_Still
William Grant Still (May 11, 1895 – December 3, 1978) was an African-American classical composer who wrote more than 150 compositions. He was the first African-American to conduct a major American symphony orchestra, the first to have a symphony (his first symphony) performed by a leading orchestra, the first to have an opera performed by a major opera company, and the first to have an opera performed on national television. He is often referred to as "the Dean" of African-American composers.
Probably my favorite of his: