McIlvaine Smith is a lifelong resident of Chester County, graduating from West Chester Henderson High School in 1968 and from West Chester University in 1995 with a degree in Elementary Education. She taught 4th grade at Penn Wood Elementary, and environmental education at the Brandywine Valley Association. She and her husband, Robert, incorporated their business, Brandywine Water Systems Inc., in 1980. Together they owned and operatedthe business until his death in 2007. Their son now owns and operates the water conditioning business. McIlvaine Smith was married to Robert for 35 years. They have two grown children, a son and a daughter, and one granddaughter.
Opposed to Chester County commissioners' attempts to raise property taxes by 36% percent and remove historic buildings to expand the courthouse, McIlvaine Smith changed her party affiliation from Republican to Democrat to run for a seat on the West Chester Borough Council, and was elected in November 2001. When she was sworn in on January 2, 2002, the Council became a full Democratic body for the first time in 100 years. She became the council's vice-president in 2004. During her tenure on the council, McIlvaine Smith chaired the Parks, Recreation & Environmental Protection Committee and the Public Works Committee and initiated a resolution to support Pennsylvania Governor Ed Rendell's Growing Greener II plan.
In 2004, McIlvaine Smith ran for the Pennsylvania House of Representatives against incumbent Republican Elinor Z. Taylor. McIlvaine Smith lost with 45 percent of the vote, but she decided to forgo running for another term on the West Chester Borough Council when her term expired in 2006 in order to seek a rematch with Taylor that November. Taylor announced in late 2005 that she would retire after the current term, and West Chester-area Republicans endorsed former West Chester Borough Councilman Shannon Royer, whom McIlvaine Smith had succeeded as Fifth Ward representative on Borough Council, to replace Taylor. McIlvaine Smith formally announced on January 17 that she was running for Taylor's now open seat, and was not opposed in the Democratic primary. She was endorsed by Progressive Majority, a national Political Action Committee that supports progressive politicians at the state and local levels. Unofficial returns on election day initially showed that Royer had won by 19 votes, however, after the counting of provisional and absentee ballots, McIlvaine Smith was declared the winner by 23 votes, giving Democrats control of the state house for the first time in 12 years and making history as the first Native American ever elected to the legislature. Pennsylvania Republicans demanded a hand recount, which ended on December 22 with Mcilivaine Smith being officially certified as the winner. She is also the majority chairwoman of the Subcommittee on Special Education. In December 2007, McIlvaine Smith was one of a few lawmakers who refused to accept a pay raise from the state, saying that she would donate her additional money to charities in her district In December 2007, Shannon Royer announced his intention to challenge McIlvaine Smith for her House seat in a rematch of their closely contested 2006 campaign. On November 4, McIlvaine Smith was re-elected by more than 2,000 votes. In November 2009, she announced that she would not run for re-election in 2010, saying that she was frustrated with the progress of the post-pay raise reform movement. For health reasons, the 2010 Democratic candidate withdrew, and McIlvaine Smith stepped in to run for re-election as State Representative for the 156th District. She was narrowly defeated for re-election by Republican Dan Truitt.
