2 . America’s first transcontinental railroad, completed 150 years ago today at Promontory Summit in Utah, connected the vast United States and brought America into the modern age. Chinese immigrants contributed greatly to this notable achievement, but the historical accounts that followed often ignored their role.

Between 1863 and 1869, as many as 20,000 Chinese workers helped build the dangerous western part of the railroad, a winding ribbon of track known as the Central Pacific. At first, the Central Pacific Railroad’s directors wanted a whites-only workforce. When not enough white men signed up, the railroad began hiring Chinese men for the backbreaking labor. Company leaders were skeptical of the new recruits’ ability to do the work, but they proved themselves not only capable but even superior to the other workers.

Chinese workers cut through dense forests, filled deep narrow steep-sided valley, constructed long trestles(高架桥) and built enormous retaining walls(防护墙) -- some of which remain complete and undamaged today. All work was done by hand using carts, shovels and picks but no machinery. However, progress came at great cost: an estimated 1,200 Chinese laborers died along the Central Pacific route.

Despite these facts, Chinese workers were often left out of the official story because of their identity of foreigners. On the transcontinental railroad's 100th birthday, the Chinese workers were still not honored. It was another fifty years later that their role was gradually highlighted. To celebrate the railroad’s 150th anniversary in 2019, the California assembly passed a resolution in 2017 to recognize and honor the Chinese railroad workers by designating May 10, 2017, and every May 10 thereafter, as California Chinese Railroad Workers Memorial Day.

3 . The printing press has a long history. It was invented in Germany by Joannes Gutenberg around 1440, and brought to England by William Caxton in the 1470s.Yet the basic technology of printing remained the same up to the end of the 18th century, requiring two men to operate a wooden screw press by hand, producing about 200 impressions an hour. The 19th century was the period in which this process was mechanised, automated, and made many times faster.

A key moment in the development of mass newspapers was the development of the steam-powered printing press, adopted by the times in 1814. The new presses were able to print per hour around five times the number produced by the machines. The editor, John Walter, had the machines fixed secretly at night, so that when his printers reported for duty the next morning the majority of them found that they were out of work. The Times went from a circulation of 5,000 a day in 1815 to around 50,000 in the middle of the century. This was not caused by the steam press, but neither could it have happened without it.

Later developments improved this effect: the Applegath machine achieved 5,000 impressions per hour, and the Hoe press, an import from the United States, reached to 20,000 impressions per hour. Increase in the speed of papermaking in this period brought down the cost of printed materials both for the producer and the customer. In 1896, the Daily Mail was sold at the cost of only half a penny, and by 1900 it was selling nearly 1,000,000 copies a day.

If print production was completely changed in those years, then so was its distribution. The appearance of the steam railway meant that for the first time newspapers could be distributed across the country on a daily basis.

4 . In most Hollywood movies, the Native American Navajos still fight on horses in the American Southwest. But during World War II, a group of Navajos made their language into weapon to protect the United States. They were the Navajo Code Talkers, and theirs is one of the few unbroken codes (电码）in military history.

Navajo was the perfect choice for a secret language. It is very complex. One vowel (元音）can have up to ten different pronunciations, changing the meaning of any word. In the 1940s, Navajo was unwritten language. No one outside of the reservation could speak it or understand it.

The Navajo Code team had to invent new words to describe military equipment. For example, they named ships after fish: lotso-whale (battleship), calo-shark (destroyer), beshloiron-fish (submarine). When a Code Talker received a message via radio, he heard a series of unrelated Navajo words. He would then translate the words into English and use the first letter of each English word to spell the message. The Navajo words tsah (needle), wol-la-chee (ant), ah-kh-di-glini (victor), and tsah-ah-dzoh (yucca) spelled NAVY.

The Code Talker kept the code a secret. They memorized everything. There were no code books. As a result, no ordinary Navajo soldiers, if captured by the enemy, could understand the code. More than 3,600 Navajos served in World War II, but only 420 were Code Talkers with the US Marines. They coded and decoded battlefield messages better and faster than any machine. They could encode, transmit, and decode a three-line English message in 20 seconds. Machines of the time required 30 minutes to perform the same job.

Even after the war the code remained top secret. When they were asked about their role, Code Talkers just said: “I was a radioman.” War movies and histories came out without mentioning them. The code was never used again and was finally declassified in 1968. Only then did the secret came out.