During his political career he held the positions of Speaker of the House and President pro tempore of the Senate.

[2] Left an orphan by the age of 9,[2] he emigrated to the U.S. along with his younger brother and two sisters to join an uncle in New York.

[3] Megler entered military service for the Civil War at Cairo, Illinois, on December 19, 1861 for the Union.

[4] During the war he saw action in the battles of Fort Henry, Donelson, Shiloh, Vicksburg and Red River.

[5] He was honorably discharged at New York in October 1865 and joined his brother, Alexander Megler, in Astoria, Oregon late that year.

[7] In 1871, Megler moved across the Columbia River to Chinook, Washington[4] to join the salmon cannery of Ellis, Jewett and Chambers as the manager.

[19] The company's continuous production of canned salmon from 1873 till 1930 made it one of the longest running canneries on the Columbia River.

Megler was elected a member of the House of Representatives of the first Washington legislature in 1889 representing Wahkiakum County, Washington, running as part of the Republican ticket, and was re-elected to the second legislature in 1891 from the newly created District 24 based in Wahkiakum County.

[20] As of 2014, he is one of only three people who have held both the positions of Speaker of the House and President pro tempore of the Senate of Washington State (the others being Howard D. Taylor and Victor Zednick).

[25] A consummate back-room deal maker who preferred to operate out of the public eye, he was known for his organizational abilities.

In 2005, the Megler Rest Area was renamed "Dismal Nitch" as part of the Lewis and Clark Memorial project, although some historians dispute that this location is in fact correctly identified.