From the projects inception in 1997 eCos has developed into widely ported, feature rich, reliable, and mature RTOS. eCos's development has been a driven by a combination of commercial interests from companies such as Cygnus, Red Hat and eCosCentric, and by eCos's open source community contributing bug fixes, ports, and new features.

eCos was conceived and initially developed by Cygnus Solutions Inc., who initiated the project in February 1997. Cygnus was at that time the leading commercial provider of the GNU compiler toolchain to the embedded market, and saw an opportunity to develop an open source based runtime partner to its open source tools.
The inaugural eCos 1.0 release was shipped in September 1998. Launch functionality included the HAL, kernel, ISO C library, and uITRON compatibility layer. Ports were provided to the MIPS, MN10300, and PowerPC architectures. Subsequent releases have continued to extend and refine the RTOS core functionality, extend the feature set, and add further board and processor ports.
The EL/IX API initiative is launched in September with the aim of providing a standardized common API between eCos and Linux. This will evolve into eCos's Posix compatibility layer. Cygnus's merger with Red Hat is announced in November 1999.
The eCos based RedBoot bootloader and debug agent is announced and released in May.
eCos 2.0 alpha is released in May under a new modified GPL open source license. Red Hat subsequently went through various reorganizations and refocused on enterprise Linux as its primary market. In April 2002 eCosCentric was created as a spin-off from Red Hat, and employed the main eCos management and development team when development at Red Hat halted in June 2002. eCosCentric's mission is to focus on providing commercial eCos development services and product lines. The CMP Embedded Brand Study 2002 indicates a market share of 3% for eCos.
eCos 2.0 beta is released in March, followed by the 2.0 final in May. eCosCentric's eCosPro line of commercially supported enhanced eCos distributions debuted in September 2003.
In January 2004 Red Hat agrees in principle to transfer its eCos copyrights and trademarks to the Free Software Foundation (FSF).
The 2005 real-time operating systems survey from CMP's Embedded Systems Programming magazine placed eCos in the top ten RTOSs by market share, with over 4% of the respondents using eCos.
The Linux Devices 2006 embedded survey shows a 5% market share for eCos. The later CMP 2006 embedded survey shows sustained growth for eCos over the previous survey, with use increasing to 6% of surveyed developers. The Sony Playstation 3 launches and incorporates an eCos-based WiFi module.
The eCos trademark was acquired by eCosCentric when it became available in February 2007. CMP's Embedded Study 2007, and EDC's Embedded Development Survey 2007 both peg eCos market share at 5-6%. Architectural support for the Altera NIOS II added to eCosPro.
The Red Hat copyright transfer along with assignments from eCosCentric and all the eCos maintainers are finally complete, resulting in the unification all of eCos's copyrights under the FSF by May of 2008. eCos architectural port of the ARM Cortex-M3 cores is released.
eCos 3.0 and eCosPro 3.0 released. The 3.0 release consolidates the numerous changes accumulated within the development repository since the last full release, and modifies source headers to acknowledge the FSF copyright. eCosPro-Yaffs middleware developed providing a reliable NAND flash file system for eCosPro. eCos used as RTOS design example within "Operating Systems: Internals & Design Principles", which is awarded the 2009 TextBook Excellence Award.
eCosPro-SecureSockets and eCosPro-SecureShell middleware provides standards-based network communications security protocols to eCosPro.
The eCos 3.1 release significantly upgrades the eCosPro Developer's kit. eCosPro adds architectural support for the microMIPS core. eCos RTOS used for the DAQ control system of the $1.5B Alpha Magnetic Spectrometer particle detector attached to the International Space Station.
NTP (Network Time Protocol) added to eCosPro along with extensive changes to time and date handling. This included future-proofing to safely handle the cases of UNIX (32-bit) clock overflow in the years 2038 and 2106, and account for NTP rollovers in 2036 and 2172.
Native fully integrated USB host stack added to eCosPro. This incorporates cdc-acm serial and mass storage class support. Apple Bonjour certified Zeroconf/mDNS networking support middleware added to eCosPro. eCos-based Russian Chibis-M satellite launched from ISS to study upper atmosphere electrical phenomena.
Native fully integrated USB device stack added to eCosPro. This incorporates class support for cdc-acm serial, cdc-eem networking and rndis networking.
eCosCentric adds ARM Cortex-M7 high performance MCU and Tile-Gx multicore architectural support to eCosPro.
eCosPro extended with SMP support for ARM Cortex-A9.