A branch of a river. See 1820.

1

1753.  We got to the big fork of said river.—C. Gist, ‘Journals,’ (1893), p. 80. (N.E.D.).

2

1817.  The Skillet-fork is also a river of similar character…. it is a dreadful country on each side of the skillet-fork, flat and swampy.—M. Birkbeck, ‘Journey in America,’ pp. 144–5.

3

1820.  Where two streams unite, the lesser is frequently termed a fork of the larger into which it empties, as the North Fork of the Saline, the Skillet Fork of Little Wabash, Smith’s Fork of Muddy.—James Hall, ‘Letters from the West,’ p. 209 (Lond.). (Italics in the original.)

4

1837.  The fork of the Nebraska, where it divides itself into two equal and beautiful streams.—W. Irving, ‘Captain Bonneville’ (1849), p. 41. (N.E.D.)

5