Coats (1950) reports that Chiginagak was smoking in 1852. Powers (1958) writes that Chiginagak was steaming, with intermittent smoke in 1852. Perhaps the original source for this event is Doroshin, who viewed Chiginagak in 1852 and described it as follows (J.B. Kisslinger translation, 1983): "This volcano, which I also saw rising from behind some mountains, has a broad crater, the southern side of which has been destroyed. Snow shows white within the crater. Smoke rises from the western slope of the mountain." This description is probably of the prominent fumaroles on Chiginagak and not a volcanic eruption.

Jaggar (1932): "A mountain to the west of Kanatak was reported fuming in March 1929, and this description might apply to Chiginagak."
However, Miller and others (1998) report that the 1929 eruption of Chiginagak was "based on a brief newspaper account of "unusual activity" at Chiginagak and 6 other volcanoes observed by the crew of a ship which probably passed no closer than 25 km." The December 14, 1929 Associated Press article does not provide further information on Chiginagak, except to say that it is "also on the mainland near Katmai."
Simkin and Siebert (1994) report the eruption as a questionable eruption in December, 1929.

From Miller and others (1998): "Mr. Odon Soeth reported observing an ash eruption in July, 1971 from Port Heiden, 100 km southwest of Chiginagak; according to Mr. Soeth, the eruption lasted only one evening."

From McGimsey and Wallace (1999): "On October 22, 1997, AVO began receiving pilot reports of increased steaming, snowmelt, and sulfur smell at Chiginagak. Residents of Pilot Point and surrounding areas also reported that they began noticing an increase in steam emissions possibly as early as mid-summer 1997. A thermal anomaly was detected on Advanced Very High Resolution Radiometer (AVHRR) imagery analyzed on October 23, 1997 [see fig. 10 in original text]. During a flight around the volcano on October 30, AVO scientists observed an enlarged area of fumarolic activity and new fumaroles at about 6,300 ft (~1,900 m), directly above the previously known fumarole site.
"AVO reported the activity at Chiginagak in the weekly update of October 31, 1997, and in updates through year's end, including GVN (Smithsonian Institution, 1997, v. 23, n. 3). Daily, and later weekly, correspondence was maintained with local residents for observations, and AVO closely monitored satellite imagery for signs of increased activity."

From McGimsey and others (2003): "In October 1997, following pilot reports of increased steaming and the presence of a thermal anomaly on satellite imagery, AVO scientists traveled by fixed-wing aircraft to the volcano and observed an enlarged area of fumarolic activity and new fumaroles on the north flank of the volcano (McGimsey and Wallace, 1999). A second observation flight was conducted on March 11, 1998. Winds were relatively calm but the areas of interest were largely obscured. However, observers noticed an absence of steam emissions from the area where the lower fumaroles had been located. Bulbous white clouds lingered above the area of the new fumaroles. A very strong sulfur smell -- much stronger than that from the fall of 1997 -- was reported, as well as a yellow color to the ice that formed on the plane's windows. AVO received no further reports until August 13, 1998, when USFWS personnel and a resident of Pilot Point [see fig. 1a in original text] observed little clouds of "black smoke" accompanied by a "greenish-yellow gas" rising from two point sources to about 500 to 1,000 ft (~150 to 300 m) above the mountain. A dusting of dark material was observed on fresh snow on the upper flanks of the volcano the next morning. On August 15, AVO detected a 30-km-long (19 mi) plume extending east from the volcano. Although the plume contained no ash signal, this was the first time a plume had been observed in satellite imagery of Chiginagak.
"On September 29, 1998, AVO conducted an airborne ultraviolet correlation spectrometer (COSPEC) flight to Chiginagak and measured between 200-300 tonnes per day of SO2 emanating from the fumarolic field. Observers reported a vigorous fumarole at an estimated 1,980 m (6,500 ft) elevation on the north flank, adjacent discolored ice and snow, and a strong sulphur smell [see fig. 8 in original text]. The weaker, second fumarole reported in October 1997 was no longer present.
"AVO described the activity at Chiginagak in the weekly updates of January 2 and 9, 1998 (continued from 1997), and August 14 and 21, 1998. Although no formal call-downs occurred, AVO shared information informally with the FAA following the August activity. AVO maintained contact with local residents and USFWS personnel throughout the year, and AVO closely monitored satellite imagery for signs of increased activity."

From Neal and others (2004): "In late December 2000, Navigation Officer Daniel Karlson contacted AVO to report observations of steaming from Chiginagak Volcano in late July and early August during NOAA operations off the Pacific coastline of the Alaska Peninsula. By their estimate, the steaming emanated from a source at approximately 5,200 ft (1,580 m) on the north flank of the volcano, approximately the position of the well-known fumarole long described for Chiginagak. Karlson noted that the cloud was white and constant much of the time, with a few episodes of increased output that extended 'several miles' downwind. He reported that the activity appeared to diminish in intensity over time, ceasing altogether in early August."

From McGimsey and others (2007): "Between November 2004 and early May 2005, a flux of heat to the summit area caused melting of more than 1.3x10^7 cubic m (4.6x10^8 cubic ft) of ice and snow filling the summit crater of Chiginagak, resulting in a 400-m wide (~1,300 ft) and 105-m deep (~350 ft) cauldron containing an acidified lake (Schaefer and others, 2005; J.R. Schaefer and others, AVO/ADGGS, written commun., 2007) (see figs. 25 and 26 in original text). In early May 2005, a catastrophic release of sulfurous, clay-rich debris and acidic water from the lake, with an accompanying acidic aerosol component, traveled 27 km (~17 mi) downstream and flowed into the Mother Goose Lake, headwaters of the King Salmon River (see figs. 27 and 28 in original text). Extensive vegetation damage occurred along the flood route and Mother Goose Lake was acidified (pH of 2.9-3.1), killing all aquatic life and preventing the annual salmon run (J.R. Schaefer and others, AVO/ADGGS, written commun., 2007). AVO volcanologists were to begin the second summer of geologic mapping and hazard assessment at the volcano, but instead responded by documenting the flooding and damage, collecting water samples, measuring water temperature, conductivity, and pH, and surveying the extensive vegetation damage with a U.S. Fish and Wildlife Service botanist. A data-logging seismometer was deployed for about one month with no significant seismicity recorded; Chiginagak currently does not have a seismic network.
"AVO issued an Information Release about the activity on August 23, 2005, shortly after the field crew arrived on site, and an account was related in the Weekly Update (August 26). A summary of preliminary findings is presented by Schaefer and others (2005)."
In the August 23, 2005 Information Release, AVO reported: "An AVO field crew reports that a 1,300 ft (400 m) wide melt-water lake has formed in the snow and ice filled summit crater at Chiginagak Volcano sometime since the last observations in August 2004. Sometime earlier this summer, the southern crater rim of Chiginagak was breached, allowing a portion of the lake to drain. The resulting lahar (a debris flow consisting of a mixture of volcanic sediment, water, and ice) left a deposit on the unnamed glacier draining the crater to the south and caused flooding of 3 to 6 ft (1 to 2 m) above normal on Indecision Creek. Volcano Creek and Mother Goose Lake, the headwaters of King Salmon River, were affected as well. Floodwaters also flowed on and through Chiginagak's southeast glacier, spilling out into an unnamed Pacific drainage leading to Chiginagak Bay. The lahar likely contained acidic water. Although we have no direct samples of the summit lake water, measurements from crater lakes at similar volcanoes have shown pH values ranging from 0 to 3, the acidity arising mainly from sulfuric acid. Vegetation damage was observed along Indecision Creek and the unnamed Pacific drainage.
"The breach in the crater rim and the ensuing lahar probably occurred in July 2005; reports from Painter Creek Lodge at this time tell of strong sulfur smells and cloudy, yellowish water in the Indecision Creek drainage.
"AVO geologists continue to investigate the event and its impacts. There are no indications that an eruption is imminent or that this event is necessarily precursory to an eruption."
Follow-up studies of the area in 2006 revealed that the drainage is still acidic.