
The Mouth of the River was dated 1876/1877 in the 1995 catalogue raisonné, being dated by comparison with Study for 'The Mouth of the River' m0589, which in its turn was dated mostly from the butterfly signature. 1 Dating by butterfly is not an exact science, and the monogram varies according to the medium; furthermore there are few watercolours from this period, and when Whistler was in Venice (late 1879 to 1880) he painted hardly any. Researchers at the Freer Gallery of Art suggest a later date, between 1881 and 1883. Again, there are few securely dated works with which to compare it, with the added complication that some watercolours painted in 1881, such as Beach scene with rocks m0855, were probably signed later. However, one, The Sea - Grey and Silver m0858, probably dating from 1881, has a marginally comparable butterfly; ones of 1882-1883 appear to be different in detail. Thus it is possible that a wider date range, of 1876/1881, should be considered.

The Mouth of the River, Freer Gallery of Art

The Mouth of the River, Freer Gallery of Art

The Mouth of the River, Freer Gallery of Art
Possibly the Mersey, near Liverpool, in north-east England, or the lower reaches of the Thames.

Study for 'The Mouth of the River', private collection

The Mouth of the River, Freer Gallery of Art
Study for 'The Mouth of the River' m0589 and The Mouth of the River m0590 were clearly painted from a similar viewpoint, and on the same day, and one may have been a study for the other.
See technical details in Whistler in Watercolour, Freer|Sackler, Washington, 2019, website.
Further details are given in MacDonald 1995 (cat. rais.) [more] (cat. no. 590).
It may well have been exhibited in Dowdeswell's in 1884 or 1886, but if so it has not been identified.
By the terms of Freer's will, it cannot be lent to another venue.
1: The watercolour is catalogued in MacDonald 1995 (cat. rais.) [more] (cat. no. 590) as '1876/7'.