Pamphlets provided individuals, interest groups, political parties, and organizations with an inexpensive way to present and disseminate views and opinions and were an important form of publication during the 19th Century. A few institutions built substantial collections of these pamphlets, but they have never been easy for researchers to find and access. Research Libraries UK (RLUK) corrected that by leading a massive cataloging project that allows scholars to locate pamphlets using a single search tool. They have also digitized more than 26,000 pamphlets from seven major UK research institutions and the collections are searchable and browsable in JSTOR.
Bristol Selected Pamphlets 1800-1899
Cowen Tracts 1603-1898
Earl Grey Pamphlets Collection 1800-1900
Foreign and Commonwealth Office Collection 1545-1900
Hume Tracts 1769-1890
Knowsley Pamphlet Collection 1792-1868
LSE Selected Pamphlets 1800-1899
Manchester Selected Pamphlets 1799-1900
Wilson Anti-Slavery Collection
I recommend reading the guides provided by the project, which describe more fully the collections and how to search them. The guides also point out that the pamphlets don’t only reveal contemporary viewpoints, they contain statistics, illustrations, maps, and other evidence that would inform your research. Because pamphlets were sometimes published in response to another publication putting forward an opposing viewpoint, tracking them can provide insight into public debates.