Charles R. Walgreen Sr. purchases the drugstore where he worked as a pharmacist in Chicago, U.S.

In 1893, Charles Walgreen arrived in Chicago, a city already crowded with over 1,500 drugstores. Despite the stiff competition, Walgreen's determination to succeed on his own led him to eventually establish his own successful pharmacy.

In 1897, Charles Walgreen became a registered pharmacist, ensuring that the pharmaceutical compounds he offered in his pharmacy met the highest standards for purity and freshness.

Walgreens was founded in 1901, marking the beginning of a long history of innovation and industry leadership in the pharmacy and retail sector.

In 1910, Charles Walgreen introduced hot food offerings at his drugstores as a way to keep his fountain open during winter and provide customers with affordable, home-cooked meals.

In 1913, Walgreens had expanded to four stores located on Chicago's South Side.

In 1916, Walgreens officially incorporated as Walgreen Co. with a total of nine drugstores.

By 1919, Walgreens had grown to 20 stores, with 19 on Chicago's South Side and one on the near north side. The company also opened its first photofinishing studio in the same year.

Although milkshakes and malted milk existed earlier, Walgreens is credited with popularizing the malted milkshake, particularly the version invented by Ivar 'Pop' Coulson in 1922.

By 1925, Walgreens had more than 65 stores and had expanded to cities like Milwaukee, St. Louis, and Minneapolis. The company went public two years later and continued to grow despite the Great Depression.

In 1927, Walgreens was listed on the New York Stock Exchange and opened its first East Coast store in New York's theater district.

The stock market crash in October 1929 and the subsequent Great Depression did not greatly affect Walgreens, which was operating 601 stores in 30 states by 1934.

By 1930, Walgreens had 397 stores with annual sales of $4,000,000. The expansion was partly due to selling prescribed alcohol, mainly whiskey, which was stocked under the counter.

In 1931, Walgreens became the first drugstore chain in the United States to advertise on radio, further promoting its brand.

After Charles R. Walgreen's death in 1939, the business was passed on to his son. This marked a generational transition within the company's leadership.

In April 1940, Walgreens merged with the Marvin Drug Co., which operated eight stores and a warehouse in Dallas.

In 1946, Walgreens purchased Sanborns, one of Mexico's largest pharmacy and department store chains, from Frank Sanborn.

A significant event in 1960 was the opening of the first Walgreens store in Puerto Rico, expanding the company's reach.

In 1975, Walgreens achieved a significant milestone by surpassing $1 billion in sales. This highlighted the company's growth and success in the pharmacy retail industry.

Walgreens stock becomes publicly traded, marking a significant financial development for the company.

In 1984, Walgreens opened its 1,000th store, marking a significant milestone in the company's expansion and growth.

In 1986, Walgreens acquired the MediMart chain from Stop & Shop.

Walgreens expands its presence by entering the Puerto Rico market, reaching a new geographical area.

In 2000, Walgreens achieved a milestone by opening its 3,000th store at Halsted and Monroe in Chicago.

Walgreens becomes the first major drugstore chain in the U.S. to put its prescriptions into child-resistant containers, enhancing safety measures.

On July 12, 2006, David Bernauer stepped down as CEO of Walgreens and was replaced by company president Jeff Rein, who later became CEO and chairman of the board.

On October 10, 2008, Jeff Rein abruptly quit as CEO and was replaced by Alan G. McNally as chairman and acting CEO.

On January 26, 2009, Gregory Wasson was named CEO of Walgreens, effective February 1, 2009.

In November 2010, Walgreens filed a trademark infringement lawsuit against Wegmans supermarket chain over the similarity of logos.

In March 2011, Walgreens acquired Drugstore.com for $409 million.

On April 20, 2012, Walgreens agreed to pay $7.9 million in a settlement with the U.S. Department of Justice for violations related to the federal Anti-Kickback Statute and the False Claims Act regarding federal health care programs.

On June 19, 2012, Walgreens paid $6.7 billion for a 45% interest in Alliance Boots.

On September 10, 2013, Walgreens announced it had acquired Kerr Drug.

On November 21, 2013, Walgreens inaugurated what is believed to be the first net zero energy store in Evanston, Illinois, equipped with wind turbines, solar panels, and a geothermal system.

On August 5, 2014, Walgreens announced that it would not relocate its headquarters to Switzerland amidst controversy.

On December 31, 2014, Walgreens and Switzerland-based Alliance Boots merged to form a new holding company, Walgreens Boots Alliance. Walgreens became a subsidiary of the new company.

On July 28, 2016, Walgreens announced the shutdown of Drugstore.com and Beauty.com to focus on its primary online platform, Walgreens.com.

On September 19, 2017, the Federal Trade Commission approved Walgreens' acquisition of Rite Aid, involving 1,932 stores for a total of $4.38 billion.

In January 2018, Walgreens agreed to pay $2.25 million to settle a lawsuit accusing the company of selling expired baby food, infant formula, and over-the-counter drugs. The lawsuit also alleged that Walgreens charged more than the advertised prices.

In June 2018, a Walgreens pharmacist in Peoria, Arizona, declined to provide medication to a woman for ending her pregnancy based on religious objections. The woman, prescribed the medication for a miscarriage, was left upset by the refusal.

In September 2018, Walgreens agreed to pay $34.5 million to resolve an SEC investigation into allegations of misleading investors about financial targets. The SEC accused former CEO Greg Wasson and CFO Wade Miquelon of negligence in providing financial estimates.

In January 2019, Walgreens Boots Alliance Inc. agreed to pay over $269 million to settle federal and state lawsuits accusing the corporation of overbilling federal healthcare programs.

In February 2020, Walgreens agreed to pay $7.5 million to settle a consumer protection lawsuit for allowing an unlicensed person to work as a pharmacist without proper background check, handling over 745,000 prescriptions and filling over 100,000 controlled substance prescriptions.

In March 2021, Walgreens settled a class action lawsuit for $4.5 million, accused of wage theft and labor law violations in California between 2010 and 2017, including rounding down employees' hours, uncompensated security checks, and failure to pay premium wages for denied meal breaks.

In September 2021, a Walgreens pharmacist in Baltimore, Maryland, mistakenly administered a full adult dosage of the Pfizer-BioNTech COVID-19 vaccine to a 4-year-old girl instead of the intended Influenza vaccine. Another incident occurred in Evansville, Indiana, where a pharmacist gave full adult dosages of the Pfizer vaccine to a 4-year-old boy, a 5-year-old girl, and their parents, causing immediate sickness.

In November 2021, a federal jury found Walgreens, along with CVS and Walmart, to have substantially contributed to the opioid crisis. This trial marked the first instance where pharmacy companies defended themselves amid the opioid epidemic.

In May 2022, Walgreens agreed to pay a settlement of $683 million to the state of Florida regarding opioid sales. Despite the settlement, Walgreens did not admit to any wrongdoing as part of the agreement.

In August 2022, the state of Tennessee filed a lawsuit against Walgreens, accusing the pharmacy chain of contributing to the state's opioid crisis by not having proper controls to prevent abuse of prescription painkillers. The lawsuit alleges that Walgreens intentionally flooded the market with excessive amounts of prescription narcotics, violating public nuisance and consumer protection laws.

In January 2023, Walgreens, following a change in FDA regulations, announced their intentions to start dispensing mifepristone, a medication abortion drug, causing political turmoil and protests.

As of June 2023, Walgreens operated almost 9,000 stores in the US but announced the closure of 150 locations by the end of the month.