Ethereum’s development stages

Ethereum’s development was planned over four distinct stages.
Frontier, Homestead, Metropolis, and Serenity

Block #0 Frontier — The initial stage of Ethereum, lasting from July 30, 2015, to March 2016.

Block #200,000 Ice Age — A hard fork to introduce an exponential difficulty increase, to motivate a transition to PoS when ready.

Block #1,150,000 Homestead — The second stage of Ethereum, launched in March 2016.

Block #1,192,000 DAO — A hard fork that reimbursed victims of the hacked DAO contract and caused Ethereum and Ethereum Classic to split into two competing systems.

Block #2,463,000 Tangerine Whistle — A hard fork to change the gas calculation for certain I/O-heavy operations and to clear the accumulated state from a denial-of-service (DoS) attack that exploited the low gas cost of those operations.

Block #2,675,000 Spurious Dragon — A hard fork to address more DoS attack vectors, and another state clearing. Also, a replay attack protection mechanism.

Block #4,370,000 Metropolis Byzantium — Metropolis is the third stage of Ethereum. Launched in October 2017, Byzantium is the first part of Metropolis, adding low-level functionalities and adjusting the block reward and difficulty.

Block #7,280,000 Constantinople / St. Petersburg — Constantinople was planned to be the second part of Metropolis with similar improvements. A few hours before its activation, a critical bug was discovered. The hard fork was therefore postponed and renamed St. Petersburg.

Block #9,069,000 Istanbul — An additional hard fork with the same approach, and naming convention, as for the prior two.

Block #9,200,000 Muir Glacier — A hard fork whose sole purpose was to adjust the difficulty again due to the exponential increase introduced by Ice Age.

In 2022-10-07, Ethereum’s block height is 15,694,029

This article is scrapped from “Mastering Ethereum”