How Old Policies Affect Today

In 1800 they had no idea what the internet was yet the Sherman Anti-Trust Act made in 1800 affect us through the internet today. How?

It was a legislation passed to break up monopolies at the time

No, not those kinds of monopolies

One of the biggest at the time was the Standard Oil Company founded by John D

It was later replaced by the Clayton Antitrust Act in 1914 and eliminated
    Price Fixing, Bid Rigging, and Market Allocation among competitors aka horizontal agreements

You can learn more about it in the Sherman Anti Trust Act section of this presentation

Modern day monopolies like
Facebook, Apple, Amazon, Google, Microsoft, Netflix, etc.
exist and are affected by this Act today

Such as the time when... 
"The House Antitrust Subcommittee determined Facebook wielded monopoly powers in social network and has maintained its position by acquiring, copying, or killing its competitors, according to a report they released" (quoted from the Sherman Anti Trust Act section of this presentation)

The report for the Democratic majority staff, handling antitrust concerns regarding Amazon, Apple, and Google's parent company Alphabet, recommend that Congress revise and consider some possible courses of action / change, including "structural separation," -the requirement of companies to split parts of their businesses up.-
    For instance, Facebook could be forced to split up from acquired services such as Instagram and
    WhatsApp, competitors they previously bought up to rid themselves of competition and to
    heighten their influential power

"The report also recommends that Congress consider any acquisition by the big tech companies to be anticompetitive unless the companies can prove that the merger would be in the public's benefit and could not be otherwise achieved."

Hope this helps