1900 La Mesa / La Mesa Springs Population est. 150; San Diego City 17,700; County 35,578 (includes today’s Imperial County)

In 1902, Mrs. Mary Ferguson joins with ladies from area to form La Mesa Women’s Club (oldest existing service club in La Mesa)

Ed Fletcher and his partner William Gross purchase the Alta Ranch from the Parke Davis heirs, will later subdivide as Grossmont Colony

San Diego speculator / developer D.C. Collier obtains Andrew Crowder’s property around La Mesa Springs including Allison’s Springs and begins to promote area for residential development
La Mesa Woman's Club
 1907 C.C. Park starts La Mesa Lumber Company (oldest existing private business in La Mesa) D.C. Collier builds original springhouse with hopes of bottling water, declares intention to hold land around springs for a public park

Park, Grable, and other investors incorporate Bank of La Mesa

La Mesa Improvement Club is formed as a civic promotional organization (will later become original Chamber of Commerce)

La Mesa Methodist Church moves to La Mesa Springs and builds new church building on southeast corner of Palm and Lemon

La Mesa Scout newspaper started as a monthly with 16-year old Wiley Magruder as editor
 Bottling Water at La Mesa Springs
 1912 February 7: La Mesa Springs votes 249 to 60 to incorporate as the City of La Mesa. City Population estimated at over 700 February 14: New City Trustees hold organizational meeting and select Dr. Charles Samson as first president (Mayor)

February 16: State recognizes incorporation of City of La Mesa

February 29: Trustees hold first business meeting, set initial ordinances and name first City Marshall, Clerk, and Treasurer
 La Mesa Population
 1920s La Mesa City Population 1,528; San Diego City 74,361; County 112,248. Grossmont Union High School District formed (1920) and building opened in 1922

1921: The La Mesa Country Club, formerly located on the hill south of SR-94 and east of SR-125 in Spring Valley, opens as 9-hole dirt golf course. It would be expanded to 18 holes in 1928.

1922: St. Martin’s Catholic Church builds original building near corner of Lookout and Normal Avenue

1923: La Mesa Theater, first building constructed exclusively for showing motion pictures opens (today it is the Gypsy Treasures costume store)

1925: Members of La Mesa, Lemon Grove and Spring Valley Irrigation District vote for $2.5 million bond act to allow for purchase of Cuyamaca Water Company. Purchase formally completed January 4, 1926
 La Mesa Irrigation Purchase
 1930s La Mesa City Population 2,513; San Diego City 147,995; County 209,659 Great Depression ends real estate boom of the 1920s, several key La Mesa developments including Windsor Hills and Fletcher Hills in foreclosure due to Mattoon Act bonds

New Deal WPA projects in La Mesa include a Senior Clubhouse (1937) and new Post Office (1940)

1937: City celebrates 25th Silver Jubilee Anniversary with special events in February
 La Mesa Post Office
 1940s La Mesa City Population 3,925; San Diego City 203,341; County 289,348

La Mesa Chamber of Commerce pushes City to rename Lookout Avenue “La Mesa Boulevard” in response to California Department of Transportation’s bypassing business district for U.S. Highway 80 using El Cajon Boulevard route

LMSV School District commissions report on status of district and plan for dealing with expected exponential growth after World War II. LMSVSD opens second school in La Mesa, Lemon Avenue Elementary, original buildings by local architects Alberto Treganza with later additions by Lloyd Ruocco and Sam Hamill

1949: La Mesans along with other Grossmont Union High School district residents vote for bonds for new “La Mesa” high school
 1950s La Mesa City Population 10,946; San Diego City 333,865; County 556,808 1950: Alvarado Highway opens from Baltimore west down through Mission Valley to U.S. Highway 395 (now SR163)

1951: Helix High School opens for first year at Grossmont High campus due to delays in financing and construction

1952: La Mesa and East County neighbors vote to create Grossmont Hospital District (later Grossmont Healthcare District), original hospital building designed by noted Los Angeles architects Perriera and Luckman opens in 1955

1951-1957: New schools opened to accommodate the growing population include Fletcher Hills (1951), Murray Manor (1954), Northmont (1957), Maryland Avenue and Briar Patch (1958)

1957: La Mesa’s youth Colt, Pony and Little League baseball teams all make their respective World Series. The Little Leaguers are runners-up and the Colts win the title. Sporting News names La Mesa “Youth Baseball Capitol of America”
 La Mesa
 1960s La Mesa City Population 29,892; San Diego City 573,224; County 1,033,011 1961: Northern Little League team from Fletcher Hills, with players from both La Mesa and El Cajon, wins Little League World Series. Grossmont Shopping Center opens in La Mesa in October 1961, only the third regional mall in the County

1962: City of La Mesa, along with Chamber of Commerce and many civic organizations undertakes year-long celebration for Golden 50th Anniversary for the self-proclaimed “City of Champions”

1964: San Diego Chargers, professional American Football League team, begins seven-year lease using La Mesa’s Sunset Park as in-season training facility location

 La Mesa Little League
 1970s La Mesa City Population 39,178; San Diego City 696,769; County 1,357,854 1974: Downtown merchants hold first Oktoberfest celebration. It will become longest continuous-running civic event in La Mesa history

1975: La Mesa Historical Society formed

1979: The initial and foundational Downtown redevelopment project, the La Mesa Springs Shopping Center opens
 La Mesa Historical Society
 1980s  La Mesa City Population 50,308; San Diego City 875,538; County 1,861,846 1987: City celebrates its 75th Anniversary Diamond Jubilee with year of special events

1989: MTDB Trolley service opens through La Mesa, first rail passenger service since 1928

 1990s La Mesa City Population 52,931; San Diego City 1,110,549; County 2,498,016

1991: Initial Fletcher Parkway development projects constructed along trolley line

1997: First annual Flag Day Parade started
 Flag Day
 2000s La Mesa City Population 54,749; San Diego City 1,223,400; County 2,813,833 2000: Ground breaking celebration for new Junior Seau Sports Complex facility at Parkway Middle School

2004: Residents pass first city bond to build new public safety facilities

2006: Fire Station 11 and Fire Administration building opens

2008: New County Library and Post Office open in La Mesa Civic Center

2010: New Police Station opened
 La Mesa Police Department
 2012 City of La Mesa Centennial “Celebrating the American Hometown” will feature a year-long celebration culminating in the “Party of the Century” in January 2013  Centennial Kick Off