The history of hashtag first started in August 2007 with the recommendation of well-known social media of Twitter. They were the first to announce and recommend usage of hashtags. When the adopters of Twitter were developing their codes and in July 2009 Twitter integrates the first application for usage of hashtags. In October 2007 hashtags take place first with the hashtag #sandiegofire.
January 2011 , Instagram integrates hashtags in their applications
June 2012, Twitter makes their first commercial in TV related to hashtags
June 2013 , Facebook supports hashtags
November 2013, with the support of hashtags Twitter becomes public company with IPO.
70% of the hashtags are generated in mobile phones and the rest 30% in computers.
A fact; a tweet with a hashtag has 55% more probabilty for more retweets.
Biz Stone ( Twitter cofounder )
Interesting, I actually never knew how it all began
Hopefully now you know , thank you for your upvote.