Sia was originally conceived by David Vorick during the Summer of 2013. He discusses the idea with Luke Champine over email, calling it “the Nimbus network.” At the HackMIT hackathon in September, David formally outlines the concept in the first draft of a whitepaper. David shares his idea with friends at college and they begin programming a prototype. Luke Champine becomes involved with the project when David asks him to review a presentation outlining the idea, now called “Bytecoin.”

In early 2014, the project is renamed once more to “Sia,” after the Egyptian god of perception, and is announced on BitcoinTalk. Seeing the positive response, David decides to turn the project into a startup company and work on Sia full-time. David and Luke apply to the Y Combinator startup accelerator in April. They make it past the initial screen and fly out to California for an interview, but are ultimately rejected. The rejection letter states: “we feel that this project will take significantly longer to build than you anticipate, and may require additional domain expertise.” (David and Luke had told the interviewers that Sia would be ready for release within three months.)

After a BitcoinTalk user fraudulently raises money using David's hand-drawn diagrams, David realizes that there is sufficient interest in Sia to raise money via crowdfunding. “Sianotes” are sold via Bitcoin and on the NXT Asset Exchange, and are later convertible to Siafunds. The crowdfund is successful, and Nebulous, Inc. is formally incorporated soon after.

Through contacts at their college's entrepreneurial center, David and Luke are introduced to Jim Pallotta, who provides Nebulous with its first traditional investment funding. Though they had originally planned to relocate to San Francisco, Jim convinces them to move to Boston, where his office is located. The team lives with Luke's parents during the Summer of 2014 while working feverishly on Sia.

Originally, Sia used Proof of Storage consensus, not Proof of Work. Hosts would be grouped into “quorums” that were jointly responsible for storing users' files. The wallet was also fully scriptable, with its own bytecode interpreter capable of arbitrary computation. However, towards the end of the Summer, David discovers some insurmountable flaws in the Proof of Storage algorithm. By this time, David was active in the Bitcoin core developer community, and his understanding of cryptocurrency's unique challenges had greatly matured. The team made the difficult decision to throw out all the existing code and start over from scratch. The new iteration of Sia was based very closely on Bitcoin, deviating only to improve its known deficiencies and to add the transaction type that enables storage contracts. This new direction is formalized in the second whitepaper, titled “Sia: Simple Decentralized Storage”, published in November 2014.

The team moves to Cambridge and works around the clock to rebuild Sia from scratch. After six months of work, the project is deemed ready for widespread release. The genesis block is created on June 6th, 2015 at 10:13 EST, and the first public beta version of Sia is made available for download.

Published in March 2015, these beta releases would be incompatible with the future releases. Files rarely finished uploading successfully. Incredibly, the blockchain was not even stored on disk; it had to be newly downloaded and stored in RAM on each start up. A fledgling GUI for Sia is developed, known as Sia-UI.

Released on May 2015. This version was incompatible with previous beta versions. The blockchain becomes persistent and users no longer have to manually forward their ports. The first iteration of the .sia metadata format is designed, allowing users to share files.

Released on June 2015. This release marks the launch of the current Sia blockchain. Siafund transactions are now possible, using the converted Sianotes from the crowdfund. A GPU miner is developed, and checksums are added to Sia wallet addresses.

Published on August 2015. Wallets are now generated with a seed phrase, but as a side effect, previous wallets become incompatible and coins need to be sent to addresses of these new wallets. Also, files uploaded on versions 0.3.x are incompatible with 0.4. Ports become automatically forwarded if the router supports UPnP. Pricing becomes more important for host selection. Improvements in the UI for file uploading. General improvement in stability.

A hardfork takes place in October 2015 at block 21000 to remove old clients from the network (0.3.3.x).

On October 2015, Nebulous creates the 'Decentralize Your Data' competition for creating a simple visual and user-friendly computer backup tool on top of the Sia network. The reward was 5,000,000 SC.

On November 2015, the independent developer In-cred-u-lous releases SiaPulse.com including hosts monitoring, a faucet and network charts and calculators.

Released on January 2016. More than 500 commits change every file in the codebase:

• Improvements for renters: folder structure for file uploading is enabled, automatic contract renewal, file redundancy repair (only if renter is online)
• Host modules are more stable, making easier not to miss the Proofs of Storage
• Network performance improvements

Published on May 2016 with more than 500 new changes. Renters are now required to form an allowance before uploading. Hosts are required to set up their folders in advance. These changes make this version incompatible with previous versions. The client now features instant startup.

On June 2016, the independent developer Xurious creates the first mining pool for Sia: SiaMining.com.

This version is published on June 2016 and represents the first stable release of Sia software.

• API forward-compatibility is ensured for every future release
• Several security updates, including DoS vectors fixes
• More stability and performance for renters is added
• 1.0.4-LTS represented the first LTS (Long Term Support) version

On July 2016, the exchange Shapeshift lists Siacoin.

On Spetember 2016, Nebulous released Sia-Antfarm as a testnet framework for Sia.

On September 2016, Nebulous receives $750,000 seed funding from Procyon Ventures, Raptor Group, Fenbushi Capital and angel investor Xiaolai Li for Sia developing (http://sia.tech/funding2016/).

On November 2016, the NAS and Sia hosting machine Minebox is presented.

This version is published on January 2017 containing several new features:

• Auto-consolidation (“defragmentation”) of small outputs in the wallets, improving funds fungibility
• Further improvements on renter’s performace, that now can store multiple TB
• Huge improvement on upload and download speeds
• Changes in the structure of the host’s Proofs of Storage

On February 2017, the independent developer and contributor Fornaxian presents this SiaWiki

On March 2017, the independent developer Sanasol intoduces the hosts explorer and network monitor SiaHub.info

On April 2017, Nebulous announced a partnership with Nextcloud, a popular open-source alternative to Dropbox and OneDrive, allowing Nextcloud users to integrate Sia as a backend.

Announced in April 2017, this release features:

• Host’s backend redesign, resulting in upgraded performance and scalability
• Instant wallet unlocking thanks to the creation of a local wallet database
• Funds can now be “swept” from one seed into another wallet
• For renters, better reporting on file’s redundancy and offline contracts

In May 2017, Bittrex and Yobit exchanges listed Siacoin.

In the lapse of two months, between March and May 2017, the market value of Siacoin increased 20x (from about 25 satoshi to more than 500 satoshi). This resulted in a considerable visibility and increase of the user base and number of transactions. The network was not ready for that volume of transactions, and as a result, the Sia software's transaction pool (mempool) began dropping transactions. Exchange wallets were not prepared for this, resulting in withdrawals that never reached their destination despite being reported as complete. The Sia development team provided exchanges with the address of mining nodes and tools to re-broadcast dropped transactions, but withdrawals were still unavailable for about three weeks. The transaction pool issues were resolved in the following release.

On June 2017, Nebulous announced Obelisk, a subsidiary company aimed at developing ASIC miners for Sia. Amid a mixed public response, Nebulous published a blog post explaining the rationale for developing ASICs.

Announced in July 2017, this release included:

• File repairing, meaning that even after a file is deleted on the renter's computer, it can still be replicated to new hosts if existing hosts go offline
• Ability to safely use the same wallet seed on multiple computers
• Faster initial blockchain download
• Improved gateway (networking code) functionality
• New API endpoints
• Transaction pool size increase and performance improvements

Also in July, the Sia Bounties program was announced to encourage the community to develop software for the Sia ecosystem, such as integrations with other popular storage providers. The first bounty of 300KS was offered for a tool that could integrate Sia with Minio. The bounty was claimed in just 2 days by GitHub user dvstate, and represents a milestone as it makes Sia compatible with popular providers as Amazon S3 or Azure and enables external file sharing.

After a reddit post by David caused public uncertainty about Sia's funding, Nebulous received a $400,000 grant from INBlockchain for the Sia development (http://sia.tech/2017grant/).

On September 2017, the second Sia Bounty is announced for achieving an integration with the popular backup serviceDuplicati. The goal is achieved on less than 48 hours by the independent developer @Fuffenz

During September 2017, the independent developers @Darval and @Rudi code a module for Sia that allows for the first time in the history of Sia to run de-centralized mining pools, using stratum support. They launched the first testing pool, "Darval Petabyte Storage". on the night of September 16th, 2017.