| 1769 | José Antonio Yorba, a young soldier in the Portolá overland expedition to Monterey, gets his first glimpse of what is today called Orange County. |
| 1810 | Rancho Santiago de Santa Ana granted to José Antonio Yorba and his nephew, Juan Pablo Peralta. |
| 1820s | Three adobe estancias constructed on bluffs overlooking the Santa Ana River to shelter wandering vaqueros. |
| 1823 | Mexico wins its independence from Spain. |
| 1848 | Mexico cedes to the United States that territory known today as the US Southwest, including all of California |
| 1868 | Rancho Santiago de Santa Ana partitioned into 73 parcels of various sizes. Further partitioning and sales continue for the rest of the century. |
| 1886 | Paularino agricultural colony established in the area along today’s Baker Street between Newport Blvd and Harbor Blvd. |
| 1887 | Boom town of Fairview springs up at what is now the intersection of Harbor Blvd and Adams Ave. |
| 1889 | Boom town of Fairview goes bust. Orange County secedes from Los Angeles County. |
| 1891 | Santa Ana and Newport Railroad begins service on tracks running down what is now Newport Blvd. |
| 1890s | Harper railroad siding established on what is now the west side of Newport Blvd opposite E 18th St.
Thurin railroad siding established between current day 22nd St and 23rd St. |
| 1899 | Santa Ana and Newport Railroad purchased by Southern Pacific. |
| 1900-03 | Drought drives most farming families, including the Harpers, off the mesa. |
| 1906 | First oil wells are drilled on the mesa, south of the present location of Newport Harbor High School.
Water reservoir built on 16th St between Orange Ave and Santa Ana Ave (present site of Heller Park). La Habra Land and Water Company (Stephen Townsend, President) subdivides 1,700 acres of Newport Heights (now the Eastside) into five-acre farms, which are then promoted by the Townsend-Dayman Investment Company of Long Beach. |
| 1907 | Townsend subdivides Newport-Mesa Tract, in what is currently known as the Westside south of 19th St.
More oil wells go up in the northern part of Newport Heights, near 21st St and 22nd St and Irvine Ave. |
| 1908 | The new town of Harper’s first school opens in a remodeled farmhouse at what is now 17th St and Newport Blvd, near where the Harp Inn is today.
Harper’s first commercial building, the Ozment General Store, is built at the northeast corner of 18th St and Newport Blvd. |
| 1909 | Grocer Ozment named first postmaster for Harper. |
| 1910 | First commercial apple orchards planted by George Waterman and George Huntington.
New two-room schoolhouse opens at the southeast corner of 17th St and Orange Ave. |
| 1913 | Fairview Farms tract opened on the Westside, between 19th St and Wilson St. (N-S) and Newport Blvd and the Santa Ana River (E-W). |
| 1915 | First permanent church, the Harper Methodist Episcopal Church, is built at southwest corner of Center St and Newport Blvd. |
| 1916 | Worst flooding by Santa Ana River since 1884. |
| 1920 | Newport Heights Co-operative Association, Fairview Farms Association and Newport Mesa Association offer a $25 prize for a new name for Harper. Former schoolteacher Alice Plumer wins with her entry, Costa Mesa.
Electricity arrives on the mesa for the first time. |
| 1922 | Bumper apple crop.
Costa Mesa Bank, the Costa Mesa branch of Bank of Balboa, opens. |
| 1923 | First sidewalks installed downtown.
First local newspaper, the Costa Mesa Herald begins operation (later this paper evolved into the Daily Pilot). Costa Mesa Grammar School opens at northwest corner of 19th St and Newport Blvd. |
| 1925 | Fred Bush elected as Costa Mesa’s first fire chief.
Frank Vaughn hired as Costa Mesa’s first police officer. Changes in weather patterns and rise of pests leads to decline of apple cultivation on the mesa. |
| 1928 | Santa Ana’s attempt to annex part of Costa Mesa defeated by five to one. |
| 1930 | Monte Vista school opens at Center St and Placentia Ave to provide “separate but equal” facilities for Costa Mesa’s Mexican children.
Newport Harbor High School completed. Rivalry emerges between Costa Mesa students and Newport Beach students. The appellation “Goat Hill” is born. So is the name “Mackerel Flats.” Great Depression begins. |
| 1932 | Costa Mesa branch of the Bank of Balboa closes. |
| 1933 | Long Beach earthquake devastates downtown Costa Mesa.
Southern Pacific branch line running down Newport Blvd is abandoned. |
| 1934 | Len Martin establishes the Costa Mesa Globe, then buys the Herald to combine it with his own paper as the Costa Mesa Globe-Herald. |
| 1936 | Early NIMBYs defeat plans to construct state prison farm off what is now Harbor Blvd. |
| 1938 | Fatal floods rampage through Orange County.
First annual Costa Mesa Scarecrow Carnival. |
| 1940 | Costa Mesa Scarecrow Carnival makes national news after local party animals kidnap a lady scarecrow and abandon her in Tijuana. |
| 1941 | Groundbreaking for United States Air Corps Replacement Training Center.
United States enters World War II. |
| 1942 | United States Air Corps Replacement Training Center redesignated the Santa Ana Army Air Base. It eventually grows to encompass 1,337 acres between Newport Blvd and Harbor Blvd where the Civic Center, Orange Coast College, Vanguard University and the Orange County Fairgrounds are today. |
| 1945 | Santa Ana Army Air Base closed. |
| 1946 | War Assets Administration sells Santa Ana Army Air Base plot to Orange Coast Junior College District.
First Lions Club Costa Mesa Fish Fry. Sky Harbor airport opens along 19th St west of Placentia. |
| 1948 | Orange Coast Junior College opens (now Orange Coast College).
Mesa Theatre cinema opens on Newport Blvd near 19th St, where Mother’s Market is today. Costa Mesa’s first park, Lions Park, opens. First local incorporation effort fails. |
| 1949 | Paulo Drive-in Theatre opens on northwest corner of Newport Blvd and Paularino St. |
| 1950 | Southern California Bible College opens (now Vanguard University). |
| 1953 | Amid annexation efforts by Santa Ana and Newport Beach, City of Costa Mesa is incorporated, encompassing most of the current city south of Mesa Dr and Wilson St, 3½ square miles.
Sky Harbor airport demolished to make way for residential development. |
| 1961 | Santa Ana Army Air Base gets a mention in Joseph Heller’s bestselling novel Catch-22. |
| 1966 | Costa Mesa Historical Society established to transform the restored Diego Sepulveda Adobe into a museum and provide docents. |
| 1967 | New Civic Center completed on Fair Drive.
Initial phases (May Company) of South Coast Plaza completed. |
| 1968 | San Diego Freeway passes through north Costa Mesa. |
| 1972 | City of Costa Mesa forms Redevelopment Agency |
| 1978 | South Coast Repertory relocates to newly-opened 4th step theater in Town Center |
| 1983 | Courtyards shopping center redevelopment opens in downtown. |
| 1986 | Orange County Performing Arts Center opens in Town Center |
| 1991 | Triangle Square redevelopment opens in downtown. |
| 1992 | 55 Freeway extended to 19th St. |
| 1998 | Fairview Park Master Plan adopted by Costa Mesa City Council |
| 1999 | City reaches 97.3% build-out. Only 218 acres remain for initial development out of a total of 8100 acres. |
| 2006 | The Renée and Henry Segerstrom Concert Hall opens in Town Center |
| 2012 | Measure V, to convert Costa Mesa to a charter city, fails to pass in the Nov. 6 general election, 13,806 yes to 20,529 no |