On July 27, 2001, the Federal Highway Administration approved plans for the Marshalls Creek Bypass.  This project would include construction of a new, four-lane limited access bypass of US 209 and PA 402, plus widening of US 209 to relieve congestion in Marshalls Creek.  The estimated price tag of the project is $70 million and was expected to begin in Spring 2005.  That was until Pyrite, which forced a halt to Interstate 99 construction on Skytop Mountain, was discovered in the path of the projected highway.  Testing is being done to determine the exact amount and remediation plans will be included in the contract proposal.

Ground was broken for the start of Phase I on August 24, 2005.  The initial $14.2 million phase will consist of preliminary grading and drainage for the PA 402 section of the bypass, as well as replacement wetlands and relocating a section of Oak Grove Drive.  Cul-de-sacs will also be built in the White Birch Estates community near Oak Grove Drive.   Three intersections are slated for improvement at US 209 at Buttermilk Falls Road, Buttermilk Falls Road at River Road, and US 209 at Winona Falls Road/River Road.  Improvements call for widening to add new turning lanes, new traffic signals, and upgrades to drainage and signage.  Phase I is expected to finish in Fall 2007.  Project website:  http://www.marshallscreekbypass.com/.

In 1965, the route's northern terminus was moved from US 22 to US 119.  In 1970, the southern terminus was moved from Johnstown at Washington Street and Clinton Street to Kantner.

Signed in 1941 on its current alignment.  In 1972, the southern terminus was moved from Susquehanna Trail to Chillisquaque.

On May 19, 2004, the southern terminus was moved from the corner of State Street and Grove Street in Clarks Summit to its current location.  The reason for the move was to create a straighter alignment for trucks that had difficulties turning from PA 407 to US 6/US 11 which resulted in congestion on the latter routes.

In 1970, the eastern terminus was moved to its current location from PA 153 just south of Interstate 80.

In 1946, the northern terminus was moved from US 309 in Sellersville via PA 153, South Perkasie Road, Blooming Glen Road, and PA 113 to its current location.  The southern terminus was moved from Buckingham to Bristol that same year.

In 1975, construction began on the Newtown Bypass and opened in 1977.

In 1940, the section from Morris to Hartfield was paved.  The western terminus was moved from US 15 in Liberty to Morris at PA 84 in 1946.

The western terminus was moved one last time from Morris to PA 44 in 1955.  In 1959, the section from Blackwell to Babb Creek was paved.

The route, surprisingly was still unpaved from Cedar Run to Blackwell until 2001 when it was paved.

The most unusual feature of PA 415 is that it splits at Harveys Lake, with each leg carrying two-way traffic.

Signed in 1966 on its current alignment

In 1946, the designation was moved to its current location.  In 1977, the southern terminus was moved from PA 77 in Spring Creek to its current location.  It took over for PA 77 from there to Garland.

Signed in 1972 from Interstate 81 in Scranton to its current southern terminus.  In 1976, upon completion of Interstate 380, the northern terminus was moved to its current location.

In 1930, the route was paved from PA 241 to Royalton and Ebenezer to Oberlin.  In 1932, the route was paved from Marietta to Bainbridge, Middletown to Highland Street, and from Oberlin to Harrisburg.  In 1935, the northern terminus was moved from 19th Street to its current location.

Construction for an interchange with I-283 and new alignment for Oberlin Road began in 1968, and concluded in 1970.

The route travels past perhaps the most famous or infamous island in North America:  Three Mile Island.  In fact, during the emergency in 1979, the Pennsylvania State Police shut down the highway in front of the plant from March 28 to April 9.

In 1930, the route's western terminus was moved from Harper Tavern to West Jonestown.  In 1936, the western terminus was moved from West Jonestown to its current location.

In 1946, the eastern terminus was moved from Schuylkill Haven to its current location.

Signed in the current location in 1964.