Federal Land Grant trackage

Of all the trackage built in the USA, what percentage was built under the Federal Land Grant? I’ve heard 8%.

If I am not mistaken the only railroads built with land grants are the UP and WP through promontory point. Other than that everything was private enterprise. Depenedent on how many miles of track are in use will determine the percentage that represents. I know that since railroad mileage has been dropping since the 1940’s it represents a higher percentage now then then.

Some basic info on this site

http://www.coxrail.com/land-grants.htm

Here is a map showing areas where land grants applied.

http://memory.loc.gov/learn/features/timeline/riseind/railroad/grants.html