You can find scores in Beeghly and other libraries using the catalogs.
In the Beeghly catalog, change the Material Type menu below the search boxes to Music Score to filter out everything but scores in your results.
The same can be done in OhioLINK by opening the advanced search and selecting Music Score in the Other Material Types menu below the search boxes.
These sites contain free scores from public domain (copyright has expired, usually pre-1923) music. The quality of the scores may vary.
Other Online Resources
These sites contain other music-related texts and associated items, such as archival materials, letters, and images.