In 1843, he founded the Copyright Club and demanded international copyright, while declaring that American writers should celebrate America in their writing. His incessant writings and speeches on the subject often made him a target from people who disagreed and he was frequently satirized and caricatured. In his A Fable for Critics (1848), James Russell Lowell referred to Mathews as a "small man in glasses" whose paranoia about his enemies has him muttering about "murderers!" and "asses!" Even those who also advocated for improving American writing found him unbearable, including anthologist/critic Rufus W. Griswold, who said his cause had infected him like a disease.
But Mathews himself complied with his own goals was a published poet, novelist, essayist, and playwright. Before his death, however, he had not published anything new in some 30 years. One Ohio newspaper referred to him as the "late Cornelius Mathews, of New York" in 1875. Today, he is best remembered for his relationships with other writers and critics rather than as a writer and critic in his own right.
Curiously, Mathews's funeral was held at St. Ann's Church at 5th and 18th in New York City, a congregation that catered to the deaf and mute. One might be curious to know if his disappearance from the public spotlight could have been due to hearing loss, though no source seems to mention it. From his 1843 poem, "The Poet":
The mighty heart that holds the world at full,
Lodging in one embrace the father and the child,
The toiler, reaper, sufferer, rough or mild,
All kin of earth, can rightly ne'er grow dull;
For on it tasks, in this late age, are laid
That stir its pulses at a thousand points;
Its ruddy haunts a thousand hopes invade,
And Fear runs close to smutch what Hope anoints.
On thee, the mount, the valley and the sea,
The forge, the field, the household call on thee...
Gather all kindreds of this boundless realm
To speak a common tongue in thee! Be thou —
Heart, pulse, and voice, whether pent hate o'erwhelm
The stormy speech or young love whisper low.
Cheer them, immitigable battle-drum!
Forth, truth-mailed, to the old unconquered field,
And lure them gently to a laurelled home,
In notes more soft than lutes or viols yield.
Fill all the stops of life with tuneful breath;
Closing their lids, bestow a dirge-like death