Agorodd Bragdy'r Rock, ar safle mae Swyddfeydd Rock Grounds y Cyngor ar hyn o bryd, ym 1850. Dim ond un o nifer o fragdai a sefydlwyd yn Aberdâr yn y bedwaredd ganrif ar bymtheg i gynhyrchu diodydd ar gyfer gwestai a thafarndai lleol oedd hwn.

Ymhlith y bragdai eraill, roedd Bragdy'r George, Bragdy'r Black Lion a Bragdy Trecynon. Roedd y tri bragdy yma wedi cau erbyn 1911. Adeg gwerthu Bragdy'r Rock ym 1921, roedd yn berchen ar 40 o dai clwm.

Dyma gynnwys y dystysgrif;

No.104
The Rock Brewery Company, Limited
Incorporated Under the Companies Act 1862 to 1893
This is to certify that John Jenkin Lewis
of The Rock Brewery Aberdare Manager is the Registered Proprietor
of two hundred Fully Paid Five-and-a-Half per Cent. Cumulative Preference Shares
of One Pound each, numbered 10181 to 10380 inclusive, in
THE ROCK BREWERY COMPANY, LIMITED, subject to the Memorandum
and Articles of Association and the Rules and Regulations of the
said Company.
Given under the Common Seal of the Company
this 16th day of June 1897