On July 25:

1956 - The Italian liner Andrea Doria sank after colliding with the Swedish ship Stockholm, 45 miles south of Nantucket Island; 51 people died.

July 26, 1775 : U.S. postal system established

On this day in 1775, the U.S. postal system is established by the
Second Continental Congress, with Benjamin Franklin as its first
postmaster general. Franklin (1706-1790) put in place the foundation
for many aspects of today's mail system.
During early colonial times in the 1600s, few American colonists
needed to send mail to each other; it was more likely that their
correspondence was with letter writers in Britain. Mail deliveries
from across the Atlantic were sporadic and could take many months to
arrive. There were no post offices in the colonies, so mail was
typically left at inns and taverns.
In 1753, Benjamin Franklin, who had been postmaster of Philadelphia,
became one of two joint postmasters general for the colonies. He made
numerous improvements to the mail system, including setting up new,
more efficient colonial routes and cutting delivery time in half
between Philadelphia and New York by having the weekly mail wagon
travel both day and night via relay teams. Franklin also debuted the
first rate chart, which standardized delivery costs based on distance
and weight.
In 1774, the British fired Franklin from his postmaster job because of
his revolutionary activities. However, the following year, he was
appointed postmaster general of the United Colonies by the Continental
Congress. Franklin held the job until late in 1776, when he was sent
to France as a diplomat. He left a vastly improved mail system, with
routes from Florida to Maine and regular service between the colonies
and Britain.
President George Washington appointed Samuel Osgood, a former
Massachusetts congressman, as the first postmaster general of the
American nation under the new U.S. constitution in 1789. At the time,
there were approximately 75 post offices in the country.

Today, the United States has over 40,000 post offices and the postal
service delivers 212 billion pieces of mail each year to over 144
million homes and businesses in the United States, Puerto Rico, Guam,
the American Virgin Islands and American Samoa. The postal service is
the nation's largest civilian employer, with over 700,000 career
workers, who handle more than 44 percent of the world's cards and
letters. The postal service is a not-for-profit, self-supporting
agency that covers its expenses through postage (stamp use in the
United States started in 1847) and related products. The postal
service gets the mail delivered, rain or shine, using everything from
planes to mules. However, it's not cheap: The U.S. Postal Service says
that when fuel costs go up by just one penny, its own costs rise by $8
million.

On July 26:

1956 - The Suez Crisis began when Egyptian President Gamal Abdel Nasser nationalized the British- and French-owned Suez Canal.

July 27 1974:

The House of Representatives charges President Richard M. Nixon with the first of three articles of impeachment
for obstruction of justice after he refused to release White House tape recordings that contained crucial information regarding the Watergate scandal.

On August 8, 1974, Nixon avoided a Senate trial and likely conviction by becoming the first president to resign.

On July 27:

1940 - Bugs Bunny made his debut in the animated cartoon "A Wild Hare."