This Google Custom Search Engine searches the Library of Congress and New York Public Library digital collections really well, and the New York Heritage and the Digital Collections of the New York State Library, Museum and Archives less well.
The New York Heritage browse page allows the researcher to view the collection by main topics, time period, or by sub-collection. Some sub-collections have topics that are easily determined and some are named for their benefactor. Items from this overall collection have been placed throughout the LibGuide according to their place in history.
A joint collection of the New York State Archives, New York State Museum & New York State Library, the collection can be browsed by topic or by sub-collection. It is also fully searchable. Depending on the item, the images will vary in ease of use and download quality.