1915 – Congress creates the Office of the Chief of Naval Operations (CNO).  Operation of the Naval Radio Service and many other means of communications are included among the responsibilities of the new office. 
The Naval radio Service is reorganized and the Navy Department establishes the Office of Communications.  Outbreak of World War I results in formation of the Naval Communication Service.  Navy appoints the first Director of Naval Communication – Captain William H. G, Bullard, USN, directly responsible to the CNO.  Naval communications is put in a state of war readiness.

October 1917 – 11 March 1935 – Cryptologic activities in the Navy were under the auspices of an organizational Entity called the Code and Signal Section of the Office of Naval Communication (ONC).

1922 – Research Desk established in Security Office of Code and Signals section of Office Department of Naval Communications (DNC).
1922 – OP-20G was established until after WWII.
1923 – CNO Request Fleet Forces listen in on enciphered foreign traffic.
1924 – RIP-5 Kana typewriter designed and 4 ordered.  Note: The RIP-5 consisted of a typewriter modified to reproduce the kana for which Japanese Morse code letters stood.  It had been developed at the initiative of Captain Laurence Safford, USN.
1924-1935- Naval cryptology service developed operational.
1925 – Department of Naval Communications (DNC) requested DCO 14th N.D. assigns one operator to copy Japanese diplomatic traffic.
1927 – Intercept statin established at Peking to copy Japanese Diplomatic traffic.
1927 – Naval Research Laboratory requested to develop HFDF equipment.
1 October 1928 – First Kana operator course started at Main Navy Building in Washington D.C.  This was the first class of On-The-Roof-Gang.
January 1931 – Experimental HFDF (Rotating Adcock) commissioned at Naval Research Laboratory.
June 1933 – Experimental HFDF developed by Naval Research Laboratory and Bell Laboratories.
August 1933 – CNO directs HFDF be installed in 1st and 12thNaval districts.
11 March 1935 – Cryptologic activities named changed to the Communications Security Group.  Also, there is an association of the so called “OP-number”, which was OP-20-G from sometime before 3 April 1923 until 10 July 1946, when OP-20-G became OP-20-2.
June 1938 – Congress authorized $85,000 for improvement Radio Facilities Corregidor.
January 1940 – Department of Naval Communications (DNC) informed on status of plans for setting up strategic HFDF stations on Midway, Johnston and Palmyra in case of emergency.
October 1940 – Cavite moved to Corregidor and Shanghai decommissioned.
November 1940 – 20-G requested immediate procurement of 20 RIP-5.
December 1940 – Strategic DF statin established at Toro Point.
May 1941 – Request 30 additional RIP-5.
July 1941 – 22 Navigational DF stations turned over to Coast Guard.
July 1941 – CNO request further development of Medium Frequency fixed Adcock DF for strategic use.
January 1942 – Intercept Station “H” moved to Wahiawa.
April 1942 – Corregidor evacuated to Melbourne.
September 1942 – School facilities at Bainbridge enlarged to accommodate 100 men.
September 1942 – School facilities at Cheltenham enlarged to accommodate 75 men.
April 1943 – $475,000 authorized or enlargement of intercept facilities at Wahiawa.
10 July 1946 – All Navy Communications Intelligence Activities were officially named Communications Supplementary Activity (CSA).  CSA’s were Deputy Chief of Communications for Communications Supplementary Activity (OP-20-2).
29 August 1947 – All Communications Supplementary Activities (CSK’s) were disestablished and became components (departments) of the parent command under the commander officer.
6 November 1948 – Head Supplementary Activity Branch, Naval Communications Division (OP-20-2) established under Captain J.N. Wenger, USN.
20 May 1949 – The Armed Forces Security Agency (AFSA) is established.
1 July 1949 – Captain E. S. L. Goodwin, USN becomes OP-20-2.
1 September 1949 – Captain John S. Holtwick, USN becomes OP-20-2.
28 June 1950 – Naval Security Group under Head Security Branch (OP-20-2) established under Captain John S. Holtwick, USN.
21 September 1950 – Naval Communications Annex Washington, 3801 Nebraska Avenue, NW, Washington, D.C. changed to Navy Security Station, 3801 Nebraska Avenue, Washington, D. C.
December 1950 – “Navy” in Navy Security Group changed to “Naval.” Navy Security Station 3801 Nebraska Avenue, NW, Washington, D.C. changed to Naval Security Station.  Naval Security Group under Chief of Naval Communications Service was commanded by Captain John S. Holtwick, USN.
July 1952 – Naval Communications Service changed to Naval Communications.
24 October 1952 – The National Security Agency was established.
21 December 1953 – Registered Publications Issuing Office (s) returned to Naval Security Group.
June 1954 – Reorganization OP-20-2 becomes OP-30-2.  OP-30-G becomes Head Naval Security Group under Captain Morrison, USN.  Captain Morrison is the first “Head” of the Naval Security Group.
May 1959 – Reorganization OP-30 becomes OP-94.  Rear Admiral Bernard F. Roeder, USN becomes OP-94-G (Head Naval Security Group).
7 July 1961 – Naval Security Group Headquarters established.  Rear Admiral Leslie R. Schulz, USN first Commanding Officer.
July 1961 – The title “Head Naval Security Group” changed to “Director Naval Security Group.”
25 September 1965 – NSGA Kamiseya, Japan fire, killing 12 Cryptologist.
8 June 1967 – USS Liberty (AGTR-5) was attacked, killing 34 men, many were Cryptologist
22 January 1968 – USS Pueblo (AGTR-2) was captured by the North Koreans.
June 1968 – Naval Security Group Command is established under a flag officer.  Rear Admiral Ralph E. Cook, USN, become first Commander.
15 April 1969 – EC-121 Begger Shadow was shot down over the Sea of Japan, off the coast of North Korea.  31 men were killed, many were Cryptologist:
12 December 1971 – RG -407 C-2A transport aircraft went down between the Philippians and Vietnam killing 10 Sailors, six were Cryptologist.
26 March 1976 – Communication Technician rating changed to Cryptologic Technician.
3 December 1979 – NSGA Sabana Seca Puerto Rico was attacked.  CTO1 John Ball and RM3 Emil White were killed and 10 others were wounded.
25 January 1987 – EA-3B went down in the Mediterranean killing CTI1 Patrick r. Price and CTI3 Craig H. Rudolf.  Five other were killed.
1995 – Relocation of Commander Naval Security Group (CNSG) HQ from Naval Security Station, Nebraska Ave in Washington D.C. to Fort Meade, MD.
1 April 2001 – Hainan Island incident with an EP-3E.
11 July 2002 – Naval Network Warfare Command (NETWARCOM) established.
2005 – Naval Security Group aligned under Naval Network Warfare Command (NETWARCOM).  Mission fundamentally changed as Navy’s lead for IO, Networks and Space.
30 September2005 – Commander Naval Security Group (CNSG) disestablished.
29 January 2010 – U.S. Fleet Cyber Command/U.S. Tenth Fleet was established.  U.S. Fleet Cyber Command is an echelon 2 command and U.S. Tenth Fleet is an echelon 3 command.  The mission is Electronic Warfare, Signal Intelligence and Cyber Operations. 
21 May 2010 – United States Cyber Command was established.
Please note that there are several other major events that have occurred that are not reported in this post.
What will the next 100 years bring?
Source: NCVA