In the Western classical music tradition we have the "song cycle", which is a collection of many short songs written by one composer as a single work. The songs are supposed to be performed all at once, in order, and either tell a single story (a setting of a long narrative poem or a number of poems by one poet), or which use different poems by different poets to explore a certain mood or emotion. Typically a song cycle is written for one singer and one piano, but there are song cycles for one singer and orchestra as well.
One famous example is Winterreise ("a journey in Winter") by the composer Franz Schubert, set to poems by Wilhelm Müller, in the German language. It was published in 1827. It is written for a male singer and piano. It consists of 24 songs and it takes more than one hour to sing the entire piece.
Schubert also set a poetic story of Wilhelm Müller's called Die schöne Müllerin ("The beautiful miller's daughter"), which also takes one hour to sing.
The song cycle has been a popular form in German-, English- and French-language music, since the mid-1800s.
Examples of well-known English-language song cycles are:
Songs of Travel from 1904 by Ralph Vaughan Williams to poems by Robert Louis Stephenson, 24 minutes in length.
Hermit Songs from 1953 by Samuel Barber to poems by several poets, 18 minutes in length
You added "Some would say the opera, but that's not English."
Excuse me, but there are thousands of operas written in English, starting about 400 years ago, just as there are thousands of operas written in French, Italian, German, Russian, and practically every other language. There were even a few operas written in Arabic in the 20th century.
Opera is a stage play which has many different actors who sing their words while they act their parts. An opera also has a chorus of singers, it usually has dancers, and much more. An opera can be anywhere from about 45 minutes to 3 hours in length.
Since your question was about a very long piece sung by a single singer, that is where "opera" does not fit into your definition. I know of no opera that uses only one singer.