Due to the government shutdown, the NGS and USGS websites are currently unavailable.
Archived NGS datasheets (from 2000-2001) are available at Geocaching.com: http://www.geocaching.com/mark/
These are useful only for benchmark hunters and are not to be considered reliable survey data.
Some USGS datasheets are available here: https://thesurveystation.com/usgs-datasheets/
NOAA’s Tides and Currents website is still active. Tidal bench mark datasheets are available here: http://tidesandcurrents.noaa.gov/stations.html?type=Bench+Mark+Data+Sheets
Local agencies’ marks may be available here: https://thesurveystation.com/local-control-monument-databases/